An analysis of magnetic reconnection events and their associated auroral enhancements

An analysis of simultaneous reconnection events in the near-Earth magnetotail and enhancements in the aurora is undertaken. Exploiting magnetospheric data from the Geotail, Cluster, and Double Star missions, along with auroral images from the IMAGE and Polar missions, the relationship between a reconnection signature and its auroral counterpart is explored. In this study of 59 suitable reconnection events, we find that 43 demonstrate a clear coincidence of reconnection and auroral enhancement. The magnetic local time (MLT) locations of these 43 reconnection events are generally located within ±1 h MLT of the associated auroral enhancement. A positive correlation coefficient of 0.8 between the two MLT locations is found. The enhancements are localized and short-lived (τ≤10 min) and are as likely to occur during the substorm process as in isolation of a substorm. No significant dependence of the reconnection or auroral enhancement location on the dusk-dawn components of the solar wind velocity (Vy), IMF (By) or local By or Vy, as measured by the reconnection-detecting spacecraft, is found

Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event.

The structure of the current sheet along the Magnetospheric Multiscale (MMS) orbit is examined during the 11 July 2017 Electron Diffusion Region (EDR) event. The location of MMS relative to the X-line is deduced and used to obtain the spatial changes in the electron parameters. The electron velocity gradient values are used to estimate the reconnection electric field sustained by nongyrotropic pressure. It is shown that the observations are consistent with theoretical expectations for an inner EDR in 2-D reconnection. That is, the magnetic field gradient scale, where the electric field due to electron nongyrotropic pressure dominates, is comparable to the gyroscale of the thermal electrons at the edge of the inner EDR. Our approximation of the MMS observations using a steady state, quasi-2-D, tailward retreating X-line was valid only for about 1.4 s. This suggests that the inner EDR is localized; that is, electron outflow jet braking takes place within an ion inertia scale from the X-line. The existence of multiple events or current sheet processes outside the EDR may play an important role in the geometry of reconnection in the near-Earth magnetotail

Development of the Virtual Earth\u27s Magnetosphere System (VEMS)

We have constructed a new research environment for geo-space science based on 3-D visualization tool and network database; Virtual Earth\u27s Magnetosphere System (VEMS). With an interactive research environment researchers can visually understand structures of the Earth\u27s magnetosphere using VEMS. On the VEMS, computer simulation results and observation data are simultaneously visualized, having a potential to data assimilation for geo-space studies in the future. Since the VEMS deals with time-dependent data, it also helps researchers to study dynamics of the Earth\u27s magnetosphere. We found that immersive data analyses are possible using the VEMS on a virtual reality system

Space Plasma Physics: A Review

Owing to the ever-present solar wind, our vast solar system is full of plasmas. The turbulent solar wind, together with sporadic solar eruptions, introduces various space plasma processes and phenomena in the solar atmosphere all the way to Earth’s ionosphere and atmosphere and outward to interact with the interstellar media to form the heliopause and termination shock. Remarkable progress has been made in space plasma physics in the last 65 years, mainly due to sophisticated in situ measurements of plasmas, plasma waves, neutral particles, energetic particles, and dust via space-borne satellite instrumentation. Additionally, high-technology ground-based instrumentation has led to new and greater knowledge of solar and auroral features. As a result, a new branch of space physics, i.e., space weather, has emerged since many of the space physics processes have a direct or indirect influence on humankind

Annual Variation of the Geomagnetic Field in Polar Regions (b. Electric Fields and Current System) (Proceedings of the First Symposium on Coordinated Observations of the Ionosphere and the Magnetosphere in the Polar Regions (Part I))

The annual variations of the geomagnetic field H and Z are studied by means of the data from worldwide stations during 1957-1964. The amplitudes and phases of the annual variations change smoothly with geomagnetic latitudes, except for the data within the auroral zones. The amplitudes of the annual variations of H and Z in the polar regions show a clear dependence on the solar cycle. The solar-cycle modulation of the amplitudes is in approximate proportion to the geomagnetic activity rather than to the sunspot number. The modulation of H is different from that of Z in some years. The amplitudes of the annual variations of H and Z in polar regions depend clearly on the north-south component of interplanetary magnetic field, B_z. When B_z is southward the amplitudes are larger in comparison with the cases of northward B_z. The B_z -dependence of the annual variation amplitudes is greater for H than for Z

Energetic Particle Observations at Synchronous Orbit : Multiple-Satellite Study for Flux Variation by GOES-2, GOES-3 and GMS and Nightside Flux Depression for Continuous Geomagnetic Activity by GMS (a. Precipitating Particles and Auroras) (Proceedings of the Second Symposium on Coordinated Observations of the Ionosphere and Magnetosphere in the Polar Regions : Part I)

This article reports the results of studying the behavior of the energetic particle flux obtained at synchronous orbit during substorms. The multi-satellite study has clearly showed that the evening particle flux decrease contrasts with the behavior in the midnight-morning side, where the energetic particle flux increases at the substorm expansion onset. Two-days' examples indicate that the flux behavior during the periods of the continued geomagnetic activities seems to be somewhat different from that for the relatively large and isolated events

キョク チイキ ニオケル チキュウ ジバ キセツ ヘンカ b. デンバ ト デンリュウ ケイ ダイ1カイ キョクイキ ニオケル デンリケン ジキケン ソウゴウ カンソク シンポジウム PART 1

極地域においては,地球磁場が顕著な年周変化を示す.世界各地における1957-1964年の地磁気H成分とZ成分観測値を用いて,この極地域独特の年周変化を研究し,中低緯度地域における地磁気年周変化との関連も併せて求めた.オーロラ帯以外の地域においては,地磁気年周変化の振幅・位相ともに磁気緯度に対してゆるやかに変化している.極地域の地磁気年周変化振幅には太陽活動周期との関係が見られるが,太陽黒点数よりは地磁気活動変に対して良い対応を示している.その際地磁気H成分とZ成分とでは影響の受け方がやや異なっている.また,極地域における地磁気年周変化振幅は,惑星間空間磁場の南北成分B_zに明らかに依存しており,B_zが南向きの時の方が,北向きの時に比べてより大きな年周変化振幅を示し,その傾向は地磁気Z成分よりもH成分の方により大きくあらわれる.The annual variations of the geomagnetic field H and Z are studied by means of the data from worldwide stations during 1957-1964. The amplitudes and phases of the annual variations change smoothly with geomagnetic latitudes, except for the data within the auroral zones. The amplitudes of the annual variations of H and Z in the polar regions show a clear dependence on the solar cycle. The solar-cycle modulation of the amplitudes is in approximate proportion to the geomagnetic activity rather than to the sunspot number. The modulation of H is different from that of Z in some years. The amplitudes of the annual variations of H and Z in polar regions depend clearly on the north-south component of interplanetary magnetic field, B_z. When B_z is southward the amplitudes are larger in comparison with the cases of northward B_z. The B_z -dependence of the annual variation amplitudes is greater for H than for Z