Here we outline some examples of the types of research projects which may be offered to undergraduates attending our summer research experience. They cover topics across our range of expertise, from photospheric magnetic fields, through particle acceleration in the solar wind, to global models of the heliosphere. For each we list the title, advisor's name and position, along with a short description of the project.
I. Title: Interstellar Neutral Atom in the Heliosphere
Adviser: Dr. Jacob Heerikhuisen (UAHuntsville Assistant Professor of Physics)
Figure 3: Cuts from a 3D heliospheric simulation showing ion
temperature (top half and neutral density (lower half).
The galactic environment surrounding the sun is known as the local interstellar medium (LISM). The interaction between the solar wind and the LISM creates the heliospheric interface, and the interstellar plasma is separated from solar wind by the heliopause. However, the LISM is only about 25% ionized. Intersellar neutral atoms can cross the heliopause and be detected in the inner heliosphere, either as atoms, or as so-called "pick-up ions" if the atom looses an electron during a charge-exchange collision. We have developed sophisticated computational models of the interaction (Fig 3). These include an MHD description of the plasma, coupled to a kinetic description of neutral (Heerikhuisen et al, 2008). In this project students will investigate the measurements of interstellar neutral atoms in the heliosphere from NASA's IBEX and CASSINI missions. This spacecraft data will then be compared to neutral atom data from 3D simulations obtained using different LISM parameterizations. The goal will be to try and interpret these spacecraft measurements of neutral atoms in terms of the 3D structure of the heliospheric interface.
II. Title: What is the Frequency of Heating Events in the Solar Corona?
Adviser: Dr. Amy R. Winebarger (MSFC Research Astrophysicist)
Figure 4: High resolution image of coronal
loops from SDO/AIA that will be analyzed
to estimate coronal heating.
In the 1930s, it was discovered that the solar atmosphere, or corona, was formed of high temperature (> 1MK) plasma, even though the solar surface was only ~6000 K. The question of how energy is transported to and released in the corona remains unsolved today, though it is most likely related to the magnetic field that creates loop structures in the corona. In this project, the student will analyze high-resolution images of coronal loops made with the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO) to determine the loops' temperature, steadiness and lifetime. The student will then use a one-dimensional hydrodynamic model to determine the frequency of heating events required to reproduce the observation. This information will put important constraints on the coronal heating mechanism.
III. Three-Dimensional Global MHD Corona-Interplanetary (COIN-TVD) Model for the Student of Coronal Mass Ejection (CME) Propagation and Interaction
Adviser: Dr. S. T. Wu (UAHuntsville Distinguished Professor Emeritus)
Figure 5: A three-dimensional representation of the CMEs
(140° < φ < 180º) shown at different times.
The 3D Global MHD COIN-TVD model (Shen et al, 2011) to be used in this project is designed in the spherical coordinate system using a total variation diminishing (TVD) scheme. This model has a domain from the solar surface to 1 AU and beyond. Observed photospheric magnetic fields (line-of-sight) and Parker's solar win solution are used as input to the MHD models.
Figure 5 illustrates the capability of this numerical model. The result is a simulation of two successive CMEs occurring on 2001 March 28. The two CMEs are represented by two magnetic blobs. The interactions of the two CME induced shocks are clearly exhibited. This project will involve analyzing output from several simulations run with known CME conditions, and comparing these to spacecraft data (e.g. STEREO) to help understand CME propagation and particle acceleration.
IV. Title: Exploring the Dichotomy of X-Ray Jets in Solar Coronal Holes: Is More Cool Plasma Ejected in Blowout Jets that in Standard Jets?
Adviser: Dr. Rom Moore (MSFC Research Astrophysicist)
Figure 6: Reconnection model of X-ray jets.
Moore et al (2010) have pointed out that two different types of X-ray jets are observed in the Sun's polar coronal holes in movies from the Hinode solar space mission: standard jets and blowout jets. In this project, Hinode coronal X-ray movies taken from the Solar Dynamic Observatory (SDO) will be searched for X-ray jets. Students will take the observed characteristics of each jet and identify it as a standard jet, a blowout jet, or indeterminate. Co-temporal movies taken by SDO in 304 Å emission from He II will then be examined for whether the identified blowout jets carry much more He II plasma than standard jets. If it is found that most blowout jets do carry more 80,000 K plasma than most standard jets, this will support the scenario for the production of polar X-ray jets depicted in Figure 6. If instead it is found that in the He II 304 Å movies most standard jets are about as visible as most blowout jets, this will challenge the models. In this way the student project will develop a statistical basis to investigate the hypothesis underlying Figure 6.
V. Title: Production of Solar Energetic Particles in a Chaotic Magnetic Field
Adviser: Dr. Brahmananda Dasgupta (CSPAR Principal Research Scientist)
Figure 7: Poincare sections of non-
chaotic (top) and chaotic (bottom)
magnetic field lines.
The magnetic fields generated in the Sun, by several mechanisms - which are not yet fully understood - is the prime agent governing the major activities of the Sun, like solar flares, coronal mass ejection, energization of particles leading to the production of solar energetic particles (SEPs). The wealth of observational data gathered by various solar missions reveals the structure of solar magnetic fields, which is extremely complex and variable in time. However, out of the complex entanglement, we try to identify some basic building blocks which fabricate these complex structures - these are current loops, current-sheets and linear elements.
We have demonstrated (Ram & Dasgupta, 2010) that chaotic magnetic field can be generated by an asymmetric current configuration and breaking of adiabatic invariants of a particle moving in such fields. In this project student will: (i) trace magnetic field lines for combinations of asymmetrically places dipoles and quadrupoles; (ii) trace particle motions in those fields; (iii) study energization of particles in the presence of a wave.
VI. Title: Experimental Investigation of Retarding Potential Analyzer Performance
Adviser: Dr. Linda Krause (MSFC Research Astrophysicist)
Figure 8: Data from PLANE showing plasma turbulence.
The Plasma Local Anomalous Noise Environment (PLANE) sensor is a bifurcated Retarding Potential Analyzer (RPA) which is capable of measuring turbulence in drifting plasma up to 10 kHz in sampling frequency. The PLANE instrument was successfully tested on the FalsomSAT-3 satellite during an ionospheric mission in which an onboard artificial plasma source was pulsed while the satellite was tumbling. Initial results demonstrated the ability for PLANE to distinguish between local versus ambient irregularities in plasma density due to the unique signature in the data during source operation.
In this REU project, students will participate in the calibration of a PLANE sensor in the presence of an oscillating plasma source. Student will be introduces to high vacuum systems necessary to produce an environment experienced by satellites, drifting/oscillating plasma source, RPA operation and data analysis techniques.
VII. Title: Sounding Rocket Instrument Testing and Calibration
Adviser: Dr. Jonathan Cirtain (MSFC Principal Research Astrophysicist)
Figure 9: Diagram of an extreme ultra-violet source used to calibrate chromospheric instrumentation.
The MSFC Heliophysics group is actively involved in the design, fabrication and testing of several sounding rocket experiments. The Solar Ultraviolet Magnetograph Instrument (SUMI) was initially launched in 2010 and is proposed to be launched again in June 2012. This instrument can measure the chromospheric magnetic field of the sun and employs new technologies for mirror thermal design and spectrograph optical design and manufacturing. The High resolution Coronal Imager (Hi-C) will be the highest resolution EUV telescope ever launched. The Marshal Grazing Incidence X-ray Spectrometer (MaGIXS) is a new instrument design concept and will be the first experiment to spatially resolve the solar x-ray spectrum. This instrument has be designed and may of the components are in the laboratory trial phase needed to demonstrate capability and determine performance. These instruments demonstrate the active development of solar space-based instrumentation and would provide a unique opportunity for hands-on experience for REU participants in calibrating instrumentation, testing and aligning optics, and analyzing both science and engineering experiment flight data.
VIII. Title: Investigating X-ray Bright Points and Jets in On-disk Coronal Holes
Adviser: Dr. Mitzi Adams (MSFC Research Astrophysicist)
Figure 10: The figure shows an example of a jet
with an associated X-ray bright point.
An X-ray bright point (XBP) is a small (5 - 60 arcsec), compact brightening, observed in coronal X-rays. Previous studies of XBPs identified that (1) about two-thirds of the global population of XBPs are created from chance merging and cancellation of pairs of wandering opposite-polarity photospheric magnetic flux, and (2) about one-third from emerging bipolar magnetic fields, so-called ephemeral active regions. Since the magnetic flux in a coronal hole is predominantly one polarity, we expect that the opposite polarity flux of an ephemeral active region is quickly canceled by the surrounding ambient flux; hence, we expect that nearly all XBPs in coronal holes are emerging ephemeral active regions, not chance-encounter bi-poles. For this project, we will test whether each identified XBP within a coronal hole located close to the central solar disk and extending close to the equator, is an emerging bi-pole or a chance-encounter bi-pole.
IX. Title: Visualization and analysis of Large, 3-D Data Sets
Adviser: Dr. Nikolai Pogorelov (UAHuntsville Professor of Physics)
Figure 11: Example of visualization with
VisIt. Here the heliopause surface is
draped by the interstellar magnetic field lines.
Visualization is not just pretty pictures. It allows us to analyze enormous amounts of data, sometimes obtained on complicated computational meshes, such as used in the adaptive mesh refinement (AMR) approach. To understand the distributions of quantities in complicated plasma flows, one needs to be able to create images of 3D surfaces, generate slices of 3D distributions, analyze the streamline and magnetic field line behavior, etc. Berkeley and Oak Ridge National Laboratories are developing a new type of software, called VisIt, capable of addressing the above issues in an efficient manner. Our research group closely collaborates with the VisIt developers by providing them input about missing features and desirable challenges. In this project students will take output from an advanced 3D time-dependent AMR simulation of the heliosphere and extract data along various spacecraft trajectories and compare these data to spacecraft measurement. Additionally, students will extract data about shocks in the simulated solar wind and use VisIt to create movies of these shock fronts as they move through the heliosphere and interact with its distant boundaries. The question of how to efficiently visualize data sets from large scale simulations or from high resolution observations is becoming more pertinent as data sets continue to ever larger.
X. Title: Exploring the Twin-CME model for large Solar Energetic Particle Events
Adviser: Dr. Gang Li (UAHuntsville Assistant Professor of Physics)
Figure 12: The cartoon depicting our "twin-CME"
scenario for generating an SEP event.
Ground Level Events (GLEs) are extreme (GeV/nucleon) Solar Energetic Particle (SEP) events. Understanding the underlying particle acceleration mechanism is a major goal for Space Weather studies. In Solar Cycle 23, a total of 16 GLEs have been identified. Most of them have preceding CMEs and in-situ energetic particle observations show some of them are enhanced in ICME or flare-like material. Motivated by this observation, Li et al (2011) proposed a twin CME model for the GLE events in which two CMEs erupt in sequence during a short period of time from the same Active Region with a pseudo-streamer-like pre-eruption magnetic field configuration. The first CME is narrower and slower and the second CME is wider and faster (Fig 12). The combined effect of the presence of the first shock and the existence of reconnection is that when the second CME erupts and drives a second shock. One finds both an excess of seed population and an enhanced turbulence level at the front of the second shock than for a single CME-driven shock, and more efficient particle acceleration will occur. Students will test the twin-CME idea by closely examining data from small gradual SEP events.
XI. Title: Transport of Galactic Cosmic Rays in the Heliosphere
Adviser: Dr. Vladimir Florinski (UAHuntsville Assistant Professor of Physics)
Figure 13: Simulation of CIR used for
cosmic ray propagation studies.
Galactic and anomalous cosmic rays are observed to experience a recurring 27-day modulation associated with solar rotation (e.g., Reames and Ng, 2001). Data indicates that intensity peaks and troughs are associated with the crossing of the heliospheric current sheet (HCS), with high intensity period associated with the magnetic field transition from outward (North) to inward (South). The effect is believe to be primarily due to drifts along the HCS in combination with cross-field transport. However, the role of corotating interaction regions (CIRs), produced by an interaction between fast and slow solar wind streams, has not been fully recognized to date. As part of this project, a student will examine and compare the patterns in 27 day modulation for the 1996 (positive) and the 2008 (negative) solar minima using Advanced Composition Explorer (ACE) data. Assisted by the adviser, the student will perform simulations of cosmic-ray transport within a CIR structure using the UAH suite of MHD and energetic particle transport codes (Florinski, 2011). A sample CIR structure (From an MHD simulation) is illustrated in Figure 13. Benefits to the student will include hands-on experience with spacecraft data and state of the art simulations.
XII. Title: Radiation Hazards in Space Due to Massive Explosions Above the Sun's Surface
Adviser: Dr. Jakobus le Roux (UAHuntsville Associate Professor of Physics)
Figure 14: Calculated spectrum of
accelerated SEPs behind a shock.
Massive explosions about the Sun's surface called coronal mass ejections (CMEs) hurl billions of tons of solar wind plasma into space at high speeds. The strongest CMEs are observed to drive fast moving shock waves in front of them that can accelerate large amounts of charged particles from solar wind, solar flare, or previous CME to energies close to the speed of light between the Sun and Earth and beyond. These solar energetic particles (SEPs), can potentially pose a radiation hazard to astronauts in the space station or astronauts involved in space travel. However, the details of how SEPs reach such high energies still elude us today. We are developing and applying sophisticated computer models of the shock acceleration process to unravel the physics of the formation of high-energy SEPs (Fig 14). Students will do a series of runs with the SEP shock acceleration code to investigate how hazardous radiation levels near Earth are increased by various competing initial shock heating processes.
XIII. Title: Reconstructing Flux Ropes From Spacecraft Measurements
Adviser: Dr. Qiang Hu (CSPAR Research Scientist)
Figure 15: Cross-section of a magnetic flux rope obtained from reconstruction.
In this project, a program package written in MATLAB (courtesy of Christian Möstl, Space Research Institute, Graz, Austria) will be utilized for learning the method and analyzing real spacecraft measurements of magnetic flux ropes and clouds in the solar wind. These programs are based on those developed by QiangHu and Bengt Sonnerup (Hu and Sonnerup, 2002). The goal is to go through the process of data acquisition, interval selection, pre-processing, final reconstruction and visualization of the result (Fig 15). One can immediately obtain the parameters of such a large-scale structure, such as the size, the direction and strength of the field, and the handedness of the helical magnetic field configuration. These are important facts in assessing its space weather effect, mainly in terms of its capability of providing strong and long-duration southward interplanetary magnetic field. Using reconstruction results students will correlate observations to their geo-effectiveness.
XIV. Title: Investigating Turbulence in the Solar Wind using Spacecraft Data
Adviser: Dr. Gary Zank (UAHuntsville Professor, Physics Department Chair, CSPAR Director)
Figure 16: The variance in magnetic
field measured by Voyager 2
Numerous outstanding problems in space physics require an understanding of the transport and dissipation of turbulence in magnetized flows. For example, the dissipation of turbulence driven by the coupling of upwardly propagating and reflected Alfven waves might be responsible for heating the solar corona in open field line regions, and may be the origin of the fast solar wind. Turbulence also helps to scatter energetic particles, such as cosmic rays and SEPs.
In this project students will build a detailed data set against which to test theoretical models. By utilizing the velocity, magnetic field, and density background and fluctuations of the solar wind measured by Voyager 1 & 2, Pioneer 1 & 2, Ulysses, and Helios spacecraft, students will construct spatial and temporal profiles of a series of quantities that the turbulence transport theories predict.
XV. Title: Bulk Properties of the Inter-planetary Medium
Adviser: Dr. Nazirah Jetha (CSPAR Post-Doc and Part-time UAHuntsville Professor)
Figure 17: Solar wind speed as a function of latitude and solarcycle from spacecraft data.
In order to be able to accurately characterize the flow and transport of instabilities in the solar wind, a clear understanding of the bulk flow properties including the magnetic field is required, so that the influence of shocks and other large-scale events can be accounted for in subsequent data analysis. Students will build a database of bulk solar wind properties, using data from spacecraft that have (or are) operated in various regions of the heliosphere (Voyager 1 & 2, Pioneer 10 & 11, Helios 1 & 2, and Ulysses). How the solar wind changes with solar cycle will also be investigated, and a data set of the solar wind useful for theoretical studies, such as the evolution of turbulence, will be made.