L. W. Blum

THEMIS measurements of quasi‐static electric fields in the inner magnetosphere

We use 4 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS) double-probe measurements to offer, for the first time, a complete picture of the dawn-dusk electric field covering all local times and radial distances in the inner magnetosphere based on in situ equatorial observations. This study is motivated by the results from the CRRES mission, which revealed a local maximum in the electric field developing near Earth during storm times, rather than the expected enhancement at higher L shells that is shielded near Earth as suggested by the Volland-Stern model. The CRRES observations were limited to the duskside, while THEMIS provides complete local time coverage. We show strong agreement with the CRRES results on the duskside, with a local maximum near L = 4 for moderate levels of geomagnetic activity and evidence of strong electric fields inside L = 3 during the most active times. The extensive data set from THEMIS also confirms the day/night asymmetry on the duskside, where the enhancement is closest to Earth in the dusk-midnight sector, and is farther away closer to noon. A similar, but smaller in magnitude, local maximum is observed on the dawnside near L = 4. The noon sector shows the smallest average electric fields, and for more active times, the enhancement develops near L = 7 rather than L = 4. We also investigate the impact of the uncertain boom-shorting factor on the results and show that while the absolute magnitude of the electric field may be underestimated, the trends with geomagnetic activity remain intact.

Evolution of relativistic outer belt electrons during an extended quiescent period

To effectively study loss due to hiss-driven precipitation of relativistic electrons in the outer radiation belt, it is useful to isolate this loss by studying a time of relatively quiet geomagnetic activity. We present a case of initial enhancement and slow, steady decay of 700 keV–2 MeV electron populations in the outer radiation belt during an extended quiescent period from ∼15 December 2012 to 13 January 2013. We incorporate particle measurements from a constellation of satellites, including the Colorado Student Space Weather Experiment (CSSWE) CubeSat, the Van Allen Probes twin spacecraft, and Time History of Events and Macroscale Interactions during Substorms (THEMIS), to understand the evolution of the electron populations across pitch angle and energy. Additional data from calculated phase space density, as well as hiss and chorus wave data from Van Allen Probes, help complete the picture of the slow precipitation loss of relativistic electrons during a quiet time. Electron loss to the atmosphere during this event is quantified through use of the Loss Index Method, utilizing CSSWE measurements at low Earth orbit. By comparing these results against equatorial Van Allen Probes electron flux data, we conclude the net precipitation loss of the outer radiation belt content to be greater than 92%, suggesting no significant acceleration during this period, and resulting in faster electron loss rates than have previously been reported.

Colorado Student Space Weather Experiment: Differential Flux Measurements of Energetic Particles in a Highly Inclined Low Earth Orbit

Dynamics of the E Geophysical Mon

Design and scientific return of a miniaturized particle telescope onboard the Colorado Student Space Weather Experiment (CSSWE) CubeSat

The Relativistic Electron and Proton Telescope Integrated Little Experiment (REPTile) is a loaded-disc collimated solid-state particle telescope designed, built, tested, and operated by a team of students at the University of Colorado. It was launched onboard the Colorado Student Space Weather Experiment (CSSWE), a 3U CubeSat, from Vandenberg Air Force Base on September 13th, 2012, as part of NASAs Educational Launch of Nanosatellites (ELaNa) program. REPTile takes measurements of energetic particles in the near-Earth environment. These measurements, by themselves and in conjunction with larger missions, are critical to understand, model, and predict hazardous space weather effects. However, miniaturizing a power- and mass-hungry particle telescope to return clean measurements from a CubeSat platform is extremely challenging. To overcome these challenges, REPTile underwent a rigorous design and testing phase. This paper highlights some of the design and testing which validates the data as a valuable contribution to the study of space weather. CSSWE uses a keep-it-simple design approach to minimize risks associated with low budget and student built missions. A coherent testing plan confirmed that the spacecraft would remain healthy and take reliable measurements in orbit. This paper also highlights the system-level design and testing that verified spacecraft performance pre and post launch. Despite the risks inherent CubeSat missions, REPTile to date has returned over 300 days of valuable science data, more than tripling its nominal mission lifetime of 90 days. Initial in-flight instrument results are presented, including engineering hurdles encountered in receiving and processing the data. Also, the preliminary scientific contributions of the mission are covered in this paper to demonstrate the capabilities of a low-budget CubeSat mission. As an affordable, robust, and simple instrument and mission design, CSSWE demonstrates that small satellites are a reliable platform to deliver quality science.

One year of on-orbit performance of the Colorado Student Space Weather Experiment (CSSWE)

The Colorado Student Space Weather Experiment is a 3-unit (10cm × 10cm × 30cm) CubeSat funded by the National Science Foundation and constructed at the University of Colorado (CU). The CSSWE science instrument, the Relativistic Electron and Proton Telescope integrated little experiment (REPTile), provides directional differential flux measurements of 0.5 to >3.3 MeV electrons and 9 to 40 MeV protons. Though a collaboration of 60+ multidisciplinary graduate and undergraduate students working with CU professors and engineers at the Laboratory for Atmospheric and Space Physics (LASP), CSSWE was designed, built, tested, and delivered in 3 years. On September 13, 2012, CSSWE was inserted to a 477 × 780 km, 65° orbit as a secondary payload on an Atlas V through the NASA Educational Launch of Nanosatellites (ELaNa) program. The first successful contact with CSSWE was made within a few hours of launch. CSSWE then completed a 20 day system commissioning phase which validated the performance of the communications, power, and attitude control systems. This was immediately followed by an accelerated 24 hour REPTile commissioning period in time for a geomagnetic storm. The high quality, low noise science data return from REPTile is complementary to the NASA Van Allen Probes mission, which launched two weeks prior to CSSWE. On September 13, 2013, CSSWE completed one year of on-orbit operations. In this talk we will discuss the issues encountered with designing and operating a cubesat in orbit. Data from the mission will be presented and discussed in the larger context of ionospheric and magnetospheric physics.