[1] Electromagnetic ion cyclotron (EMIC) waves play an important role in magnetospheric dynamics and their global distribution has been of great interest. This paper presents the distribution of EMIC waves over a broader range than ever before, as enabled by observations with the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft from 2007 to 2010. Our major findings are: (1) There are two major peaks in the EMIC wave occurrence probability. One is at dusk and 8-12 R E where the helium band dominates the hydrogen band waves. The other is at dawn and 10-12 R E where the hydrogen band dominates the helium band waves. (2) In terms of wave spectral power the dusk events are stronger (≈10 nT 2 /Hz) than the dawn events (≈3 nT 2 /Hz). (3) The dawn waves have large normal angles (>45 ) in the hydrogen band and even larger normal angles (>60 ) in the helium band. The dusk waves have small normal angles (≤30 ) in both the hydrogen and helium bands. (4) The hydrogen band waves at dawn are weakly left-hand polarized near the equator, become linearly polarized with increasing latitude and eventually weakly right-hand polarized at high latitudes whereas the helium band waves at dawn are linearly polarized at all latitudes. Dusk waves in both bands are strongly left-hand polarized over a wide range of latitude. Based on the linear EMIC instability model presented by Horne and Thorne (1994), we suggest that the main underlying factor for the observed spatial variations of these wave properties would be local density of cold plasma and chemical abundance. In addition, the distinct properties of H and He band waves found in this study would deserve a new attention in relation to EMIC wave generation mechanisms.

With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform ( www.spedas.org ), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have “crib-sheets,” user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer’s Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its “modes of use” with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans. Electronic Supplementary Material The online version of this article (10.1007/s11214-018-0576-4) contains supplementary material, which is available to authorized users.

[1] We statistically examine the occurrence rate of electromagnetic ion cyclotron (EMIC) waves observed by Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE). We use the 8 Hz magnetic field data set that covers the whole CCE mission period of nearly 4.5 years from August 1984 to January 1989, which is more than three times the period studied by Anderson et al. [1992] (~452 days). The large data volume allows us to evaluate the storm phase dependence of the spatial occurrence pattern of EMIC waves. The major results of this study are summarized as follows. (a) The occurrence rate is below 5% on the nightside at all L. On the dayside, the rate is <5% in the inner magnetosphere (L < 6), while it is higher than 5% in the outer magnetosphere (L ≥ 6), up to 25%. The highest rate appears in the afternoon sector. (b) The overall occurrence rate is higher for H-band events than He-band events, except for the opposite feature seen in the inner magnetosphere on the early afternoon-to-post midnightside (L < 6, 14 h < MLT < 22 h). (c) H-band events occur frequently in the outer magnetosphere (L ≥ 7) in the afternoon sector, regardless of geomagnetic activity. Under quiet conditions, H-band events also occur in the outer magnetosphere on the morningside (4 h ≤ MLT < 8 h). (d) He-band events frequently occur in the inner magnetosphere (L < 7) on the prenoon to duskside (10 h ≤ MLT < 19 h) under disturbed conditions (Dst ≤ À50 nT). (e) The storm time He-band waves are generated more frequently during the main phase than the recovery phase, with the main-phase wave excitation seen toward the afternoonside outer magnetosphere (L > 7). The results indicate two independent major processes that cause EMIC wave excitation in the Earth's magnetosphere: one externally triggers H-band waves on the dayside, and the other internally excites He-band waves on the dusk-to-afternoonside. We suggest that the former is due to solar wind compression which leads to perpendicular adiabatic ion heating and in turn an increase in temperature anisotropy, and that the latter is caused by injections of new, highly energetic ion population from the plasma sheet, with its velocity distributions becoming pancake-like on the dusk-to-afternoonside. The frequent occurrence seen on the afternoonside, at a wide L range, and during the main/development phase, strongly suggests the significant role of the sunward surge of the plasmasphere and plasma plumes in the injection-associated (i.e., storm time) EMIC wave generation.Citation: Keika, K., K. Takahashi, A. Y. Ukhorskiy, and Y. Miyoshi (2013), Global characteristics of electromagnetic ion cyclotron waves: Occurrence rate and its storm dependence,

Auroral substorms, dynamic phenomena that occur in the upper atmosphere at night, are caused by global reconfiguration of the magnetosphere, which releases stored solar wind energy. These storms are characterized by auroral brightening from dusk to midnight, followed by violent motions of distinct auroral arcs that suddenly break up, and the subsequent emergence of diffuse, pulsating auroral patches at dawn. Pulsating aurorae, which are quasiperiodic, blinking patches of light tens to hundreds of kilometres across, appear at altitudes of about 100 kilometres in the high-latitude regions of both hemispheres, and multiple patches often cover the entire sky. This auroral pulsation, with periods of several to tens of seconds, is generated by the intermittent precipitation of energetic electrons (several to tens of kiloelectronvolts) arriving from the magnetosphere and colliding with the atoms and molecules of the upper atmosphere. A possible cause of this precipitation is the interaction between magnetospheric electrons and electromagnetic waves called whistler-mode chorus waves. However, no direct observational evidence of this interaction has been obtained so far. Here we report that energetic electrons are scattered by chorus waves, resulting in their precipitation. Our observations were made in March 2017 with a magnetospheric spacecraft equipped with a high-angular-resolution electron sensor and electromagnetic field instruments. The measured quasiperiodic precipitating electron flux was sufficiently intense to generate a pulsating aurora, which was indeed simultaneously observed by a ground auroral imager.