Penetration Of Electric Field Research Articles

Response of Thermospheric Nightglow Emissions Over the Magnetic Equator to Prompt Penetration Electric Field Events

AbstractThis study examines the response of the nighttime thermosphere‐ionosphere system (TIS) over a dip equatorial station, Trivandrum (8.5°N, 77°E, 0.5° dip latitude) to prompt penetration electric field (PPEF) events occurred on 5 January 2016 and 6 March 2016. The investigation is based on nightglow emission measurements at wavelengths OI 777.4 nm, OI 630.0 nm, and OI 557.7 nm using a multiwavelength nighttime photometer. These emissions emanate from different altitude regions of the TIS, that is, 557.7 nm from ~100 km, 630.0 nm from ~220 km, and 777.4 nm from ~350 km. It has been observed that, during the westward PPEF event, the intensities of 777.4‐ and 630.0‐nm nightglow emissions enhance, whereas during the eastward PPEF event the intensities decrease. Similarly, though it is not very prominent, 557.7‐nm emission also exhibits a small enhancement/decrease during the westward/eastward PPEF events. The ionospheric base height obtained from a collocated digital ionosonde shows that during the eastward (westward) PPEF event the ionospheric layer moves upward (downward). The downward (upward) layer movement increases (decreases) the plasma density in the centroid of these airglow emissions, which in turn enhances (decreases) the emission rates. The study demonstrates the coupling between interplanetary medium and neutral TIS during nighttime PPEF events.

Reconstruction of 2D/3D ionospheric disturbances in high-latitude and arctic regions during a geomagnetic storm using GNSS carrier TEC: a case study of the 2015 great storm

On 2015 March, a G4-level geomagnetic storm hit the earth and then triggered global ionospheric disturbances. A considerable number of studies have been published showing various ionospheric responses in low- and mid-latitude regions. In contrary, very limited efforts have been made on high-latitude or polar regions. Therefore, this paper reconstructed and investigated the 2D/3D ionospheric disturbances in high-latitude and arctic regions during this great storm using multiprocessing methods. First, four longitudinal global navigation satellite system stations’ sectors are selected on Polar area, and the second-order differential of total electron content (dTEC) of each sectors is calculated to detect the ionosphere anomaly during the time of interests. Compared with the “auroral oval” distribution and the precipitating of auroral electrons data from Defense Meteorological Satellite Program, the triggering mechanism of the detected anomaly is discussed. Second, based on the dTEC detection results and the auroral electrojet index series, two disturbances processes have been identified. Then, a new computerized ionospheric tomography (CIT) algorithm called MFCIT (CIT with mapping function) is introduced, and the 3D ionosphere images under daytime (LT06:00–LT06:30) and nighttime (LT21:00–LT22:00) over Alaska are individually inverted at the temporal resolution of 1 min. In contrast with magnetic field lines distribution, the relationship between disturbances and geomagnetic fields has been analyzed. Last, two vertical electron motions are monitored with the CIT images. As the two motions occur at two different steps of the geomagnetic storm, the characteristics and amplitudes of the vertical movements can be distinguished. The physical mechanisms for the vertical motions are discussed. The upward vertical motion during the first disturbance may be induced by the eastward abnormal penetration electric field, while the second disturbance may be the outcome of the combined influences of the abnormal electric field and the precipitating of auroral electrons.

Morphology of Nightside Subauroral Ionospheric Convection: Monthly, Seasonal, Kp, and IMF Dependencies

AbstractIn this study we have used 7 years (2011–2017) of quiet (Kp ≤ 2+) to moderately disturbed (Kp = 3) time nightside line‐of‐sight measurements from six midlatitude Super Dual Auroral Radar Network radars in the U.S. continent to characterize the subauroral convection in terms of magnetic latitude, magnetic local time, month, season, Kp, and the interplanetary magnetic field (IMF) clock angle. Our results show that (1) the quiet time (Kp ≤ 2+) subauroral flows are predominantly westward (20–90 m/s) in all months and become meridional (−20–20 m/s) near dawn and dusk, with the flows being the strongest and most structured in December and January. (2) The Kp dependency is prominent in all seasons such that for higher Kp the premidnight westward flow intensifies and the postmidnight eastward flow starts to emerge. (3) Sorting by IMF clock angle shows Bz+/Bz− features consistent with lower/higher Kp conditions, as expected, but also shows distinct differences that are associated with By sign. (4) There is a pronounced latitudinal variation in the zonal flow speed between 18 and 2 magnetic local time in winter (November to February) that exists under all IMF conditions but is most pronounced under IMF Bz− and higher Kp. Our analysis suggests that the quiet time subauroral flows are due to the combined effects of solar wind/magnetosphere coupling leading to penetration electric field and the neutral wind dynamo with the ionospheric conductivity modulating their relative dominance.

Geomagnetic conjugate observations of ionospheric disturbances in response to a North Korean underground nuclear explosion on 3 September 2017

Abstract. We report observations of ionospheric disturbances in response to a North Korean underground nuclear explosion (UNE) on 3 September 2017. By using data from IGS (International GNSS Service) stations and Swarm satellites, geomagnetic conjugate ionospheric disturbances were observed. The observational evidence showed that UNE-generated ionospheric disturbances propagated radially from the UNE epicenter with a velocity of ∼280 m s−1. We propose that the ionospheric disturbances are results of electrodynamic process caused by LAIC (lithosphere–atmosphere–ionosphere coupling) electric field penetration. The LAIC electric field can also be mapped to the conjugate hemispheres along the magnetic field line and consequently cause ionospheric disturbances in conjugate regions. The UNE-generated LAIC electric field penetration plays an important role in the ionospheric disturbances in the region of the nuclear test site nearby and the corresponding geomagnetic conjugate points.

Global Ionospheric Current System Associated With Penetration Electric Field and New Mechanism for the Generation of Dayside Westward Electric Field at Low Latitudes During Northward IMF

AbstractIt is well known that penetration and shielding electric fields are related to the southward and northward turnings of the interplanetary magnetic field (IMF). The shielding electric field is assumed to be caused by the region‐2 field‐aligned currents. We have analyzed observations of equatorial ionospheric plasma drifts measured by the Jicamarca incoherent scatter radar and global ground magnetic perturbations in an event when the IMF fluctuates between southward and northward. The vertical plasma drifts/zonal electric fields in the dayside equatorial ionosphere are well correlated with the IMF reorientations, indicating that the disturbance electric fields in the equatorial ionosphere are caused by the IMF. Magnetometer data are used to reconstruct the global ionospheric currents and convection. The DP 2 current system consists of a large vortex in the afternoon‐evening sector and a much smaller vortex in the dawn sector, and the ionospheric currents associated with the dayside penetration electric field extend into the postmidnight sector. The downward plasma drift and southward magnetic perturbations at equatorial latitudes during northward IMF are correlated with the reverse convection in the polar cap, indicating that the polar electric field associated with the reverse convection is an important source of the westward electric field in the dayside equatorial region. A new mechanism is proposed to explain the generation of westward electric field in the dayside equatorial ionosphere during northward IMF.

(Invited) 2D Materials for Nanoelectronics: Prospects and Materials Integration Challenges

The size reduction and economics of integrated circuits, captured since the 1960’s in the form of Moore’s Law, is under serious challenge. Current industry roadmaps reveal that physical limitations include reaching aspects associated with truly atomic dimensions, and the cost of manufacturing is increasing such that only 2 or 3 companies can afford leading edge capabilities. To address some of the “conventions;” material’s physical limitations, “2D materials” such as graphene, phosphorene, h-BN, and transition metal dichalcogenides have captured the imagination of the research community for advanced applications in nanoelectronics, optoelectronics, and other applications. [1,2] Among 2D materials “beyond graphene,” some exhibit semiconducting behavior, such as transition-metal dichalcogenides (TMDs), and present useful bandgap properties for applications even at the single atomic layer level. Examples include “MX2”, where M = Mo, W, Sn, Hf, Zr and X = S, Se and Te. In addition to the potentially useful bandgaps at the monolayer thickness scale, the atomically thin layers should enable thorough electric field penetration through the channel, thus enabling superior electrostatic control. Further, with such thin layers, the integration with suitable gate dielectrics can result in a mobility enhancement. Applications “beyond CMOS” are also under exploration. From an interface perspective, the ideal TMD material may ne expected to have a dearth of dangling bonds on the surface/interface, resulting in low interface state densities which are essential for efficient carrier transport. The ideal TMD materials have much appeal, but the reality of significant densities of defects and impurities will surely compromise the intrinsic performance of such device technologies. This presentation will examine the state-of-the-art of these materials in view of our research on semiconductor device applications, and the challenges and opportunities they present for electronic and optoelectronic applications. [3,4] This research was supported in part by the Semiconductor Research Corporation (SRC) NEWLIMITS Center and NIST through award number 70NANB17H041 and the Erik Jonsson Distinguished Chair at the University of Texas at Dallas.

VHF Scintillation and Drift Studied Using Spaced Receivers in Southern Taiwan

AbstractA statistical study of the occurrence and drift characteristics of Very High Frequency (VHF) amplitude scintillations during 2015–2017 based on the observations of recently installed spaced receiver system at Pingtung in Southern Taiwan is presented in this paper. Drift characteristics during quiet periods have been examined in details and compared with the drift recorded during 08 September 2017 geomagnetic storm. Analysis of the recorded observations indicated a strong dependence of VHF scintillation on the solar activity level. Equinoctial asymmetry in the occurrence of VHF scintillation was seen in 2015 and 2016. However, such asymmetry was not apparent in 2017 (low solar flux). Quiet period spaced receiver drift indicated a gradual reduction in the zonal drift of irregularities between postsunset and postmidnight period. Intriguingly, the average quiet period drift of irregularities was found to be independent of solar activity level. A few investigations in recent past have already reported similar observations and can be generally attributed to the polarization process inside equatorial plasma bubbles; however, a definite explanation for this behavior is not available. During the active phase of the 08 September 2017 geomagnetic storm, a complex interplay of disturbance dynamo and prompt penetration electric field was observed in the spaced receiver derived drift velocity of ionospheric irregularities. Approximately −200% deviation from quiet period drift was observed during this moderate storm. A significant enhancement to the spaced receiver derived characteristic random velocity, Vc, was also seen during the active phase of storm, which indicates that the drift of irregularities was highly turbulent.

Solar quiet variation of the horizontal and vertical components of geomagnetic field using wavelet analysis

The solar quiet (Sq) variations of horizontal and vertical (SqH and SqZ) components of the geomagnetic field obtained from both the Northern Hemisphere and Southern Hemisphere of the International Real-Time Magnetic Observatory Network (INTERMAGNET) during solar maximum year 2001 were investigated. The results show enlargement of the SqH component of the geomagnetic field during the daytime, attributed to equatorial electrojet (EEJ) current closer to the geomagnetic equator at the electrojet stations (BNG and MBO), which are produced from large eastward flow of the current. It was observed that SqZ is positive at the southward and negative at the northward hemispheres. SqZ is amplified at HER and HBK around the daytime. Wavelet power spectrum based approach was employed to analyse the SqH, SqZ, and rate of induction (SqZ/SqH) time series in a sequence of time scaling from January to December. The higher energy of SqH and SqZ of the wavelet coefficients is noticeable at high frequency. The monthly variation rate of induction (SqZ/SqH) analyses during the Sq variations are associated with the influence of equatorwards penetration of electric fields from the field-aligned current, Earth conductivity, effect of the ocean, and ionospheric conductivity.

Influence of Quantum Capacitance on Charge Carrier Density Estimation in a Nanoscale Field-Effect Transistor with a Channel Based on a Monolayer WSe2 Two-Dimensional Crystal Semiconductor

A critical analysis of charge carrier statistics influenced by quantum capacitance is carried out in order to predict the electrical performance of a nanoscale metal–oxide–semiconductor field-effect transistor (MOSFET) with a channel made of a monolayer tungsten diselenide (WSe2) two-dimensional (2D) crystal semiconductor. Since quantum capacitance originating from two-dimensional electron gas in a quantum well or an inversion layer does not completely screen the quasistatic electric field during applied gate voltage, the partial penetration of an external electric field through the 2D semiconductor channel will generate excess charge carriers; thus quantum capacitance will play an important role in determining the overall charge carrier density in the channel. Therefore, common methods used to extract charge carrier density in the channel for three-dimensional (3D) crystal semiconductors will yield inaccurate results when used for 2D crystal semiconductors. To address this issue, this study proposes a modified approach for extracting charge carrier density in WSe2-based 2D semiconductors by combining the appropriate carrier statistics with consideration of quantum capacitance. In addition, the study investigates the effect of interface traps on overall capacitance, which may influence the electrical performance of a nanoscale MOSFET with monolayer WSe2 as a channel material.

Ionospheric disturbances at low and mid-low latitudes of the South American sector during the March 2015 great storm

This paper analyzes the response of the near equatorial and low latitude ionosphere of the South American sector to the geomagnetic storm occurred on 17 March 2015. Ionosonde data from Ramey (18.5° N, 292.9° E), Jicamarca (12.0° S, 283.2° E), Boa Vista (2.8° N, 299.3° E), Sao Luis (2.6° S, 315.8° E), Fortaleza (3.9° S, 321.6° E) and Cachoeira Paulista (22.7° S, 315.0° E) are used for the study. The results show negative disturbances in foF2 at low latitudes during the main phase of the storm, which were attributed to prompt penetration electric fields. Thus, the Equatorial Anomaly (EA) started to reduce their structure in this sector since on 17 March. During the recovery phase (on 18 March), positive disturbances were observed at low, mid-low latitudes (in the post-midnight – predawn hours), which can be mainly attributed to enhanced storm-time neutral winds and composition changes (i.e., increase in the O/N2 ratio). Disturbance dynamo electric fields would also contribute in modulating the electron density of the EA during this storm period.

Merging of Storm Time Midlatitude Traveling Ionospheric Disturbances and Equatorial Plasma Bubbles

AbstractPostsunset midlatitude traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) were simultaneously observed over American sector during the geomagnetic storm on 8 September 2017. The characteristics of TIDs are analyzed by using a combination of the Millstone Hill incoherent scatter radar data and 2‐D detrended total electron content (TEC) from ground‐based Global Navigation Satellite System receivers. The main results associated with EPBs are as follows: (1) stream‐like structures of TEC depletion occurred simultaneously at geomagnetically conjugate points, (2) poleward extension of the TEC irregularities/depletions along the magnetic field lines, (3) severe equatorial and midlatitude electron density (Ne) bite outs observed by Defense Meteorological Satellite Program and Swarm satellites, and (4) enhancements of ionosphere F layer virtual height and vertical drifts observed by equatorial ionosondes near the EPBs initiation region. The stream‐like TEC depletions reached 46° magnetic latitudes that map to an apex altitude of 6,800 km over the magnetic equator using International Geomagnetic Reference Field. The formation of this extended density depletion structure is suggested to be due to the merging between the altitudinal/latitudinal extension of EPBs driven by strong prompt penetration electric field and midlatitude TIDs. Moreover, the poleward portion of the depletion/irregularity drifted westward and reached the equatorward boundary of the ionospheric main trough. This westward drift occurred at the same time as the sudden expansion of the convection pattern and could be attributed to the strong returning westward flow near the subauroral polarization stream region. Other possible mechanisms for the westward tilt are also discussed.

Global ionospheric scintillations revealed by GPS radio occultation data with FY3C satellite before midnight during the March 2015 storm

Global observations of S4 amplitude scintillation index by the GPS Occultation Sounder (GNOS) on FengYun-3 C (FY3C) satellite reveal global dynamic patterns of a strong pre-midnight scintillations in F-region of the ionosphere during the St. Patrick’s Day geomagnetic super storm of 17–19 March 2015. The observed strong scintillations mainly occurred in the low latitudes, caused by equatorial plasma bubbles. During the main storm phase (March 17), the scintillations were first triggered in the New Zealand sector near 160°E longitudes, extending beyond 40°S dip latitude. They were also enhanced in the Indian sector, but significantly suppressed in East Asia near 120°E longitude and in Africa around 30°E longitude. During the initial recovery phase (March 18–19), the global scintillations were seldom observed in GNOS data. During the later recovery phase (after March 19), the scintillations recovered to the pre-storm level in Indian, African, and American sectors, but not in East Asian and any of Pacific sectors. These results closely correlate with observations of the density depletion structures by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite, and ground-based instruments. Such consistency indicates reliability of our scintillation sensing approach even in a case-by-case comparison study. The prompt penetration electric field and disturbance dynamo electric field are suggested as the main factors that control the enhancement and inhibition of the scintillations during the storm, respectively.

Variability of VTEC Gradient and TEC Rate Index Over Kisumu, Kenya During Selected Quiet and Storm Days of 2013 and 2014

Vertical Total electron content (VTEC) gradient or rate of change of TEC (ROT) and total electron content (TEC) rate index or rate of change of TEC index (ROTI) can directly be estimated from receiver independent exchange (RINEX) data and can be used to estimate presence and intensity of ionospheric irregularities. In this paper we present results of the variation of ROT and ROTI over Kisumu, Kenya (Geomagnetic coordinates: 9.64°S, 108.59°E; Geographic coordinates: 0.02°S, 34.6°E) for both selected quiet and disturbed conditions between 1^st January 2013 and 31^st December 2014 using data derived from NovAtel GSV4004B SCINDA-GPS receiver at Kisumu as a step in establishing ionospheric irregularities over Kisumu, Kenya during a high solar activity period of solar cycle 24. ROT was calculated from filtered average daily VTEC data within intervals of 120 seconds while ROTI was computed over 4 minutes window from ROT. ROT and corresponding ROTI for the selected quiet and storm days were plotted against universal time (UT). The presence and intensity of irregularities on the selected quiet and storm days of the years 2013 and 2014 were determined by checking ROT fluctuations and the corresponding ROTI values from the plots. The obtained results showed increased fluctuation of ROT corresponding with large ROTI values after sunset. The selected storm days of the years 2013 and 2014 had higher ROTI values than the selected quiet days of the years 2013 and 2014. The higher ROTI values during the selected storm days may be attributed to the impact of geomagnetic storms brought about by several competing dynamics including Prompt penetration electric field (PPEF), disturbance dynamo electric field (DDEF) and reduction in electron density due to increased recombination rates. The high ROTI values after sunset were a manifestation of post-sunset plasma irregularities. The obtained results also showed a diurnal trend for ROT and ROTI where ROT increased steadily from 0.00UT to around 12:00UT before falling and having an increased fluctuation between 18:00UT and 20:00UT. This corresponded well with low ROTI values between 0:00UT and 16:00UT followed by high ROTI values between 18:00UT and 20:00UT. The diurnal variability of ROT might have resulted from variation of TEC and which was attributed to changes in the intensity of incoming solar radiation.

Behavior of the Total Electron Content over the Arctic and Antarctic sectors during several intense geomagnetic storms

In this paper, the behavior of TEC at three stations located in the Arctic and Antarctic sectors during some intense geomagnetic storms in the period 2012–2016 is analyzed. The results show the opposite storm effects in the Arctic and Antarctic regions. Both the positive and negative TEC disturbances presented more fluctuations over the Arctic stations than over the Antarctic stations. Moreover, the positive TEC disturbances were more significant in winter. The negative disturbances were generally long-lasting, sometimes interrupted by short-duration positive disturbances. Overall, the increases and decreases in TEC can be mainly attributed to changes (i.e., increase and decreases in the O/N2 ratio respectively) in the thermospheric composition, but prompt penetration electric field could be responsible for the initial TEC disturbances. The thermospheric circulation and the disturbance dynamo, which are maintained due to prolonged high-energy input at high latitudes, can also play important roles at the end of main phase and during recovery phase.

Signatures of Sudden Storm Commencement on the equatorial thermospheric dayglow

It has been observed that the OI 630.0 nm dayglow emission over a dip equatorial station, Trivandrum (8.5° N, 77° E, dip 0.5° N), India registered an abrupt increase of ~ 2000 R during the compression phase of the magnetosphere as dictated by a sudden increase in solar wind ram pressure. Furthermore, an unusual depletion of these emissions has been observed during the eastward interplanetary electric field (IEF), concomitant with southward excursion of IMF Bz. The ionosonde and magnetometer observations confirmed the effects of prompt penetration electric field (PPEF). Associated with the eastward PPEF, formation of F3 layers were also noticed. These unique results, which emphasize the effect of Sudden Storm Commencement/IEF on these equatorial daytime airglow emissions are discussed in context of changes in the equatorial zonal electric field and F region height variations associated with polar/auroral activities due to the magnetosphere-ionosphere coupling.

Numerical investigation of the current transition regimes in nanochannels.

The concentration polarization phenomena and its effects represent one of the main challenges for the optimal operation of many nanofluidic systems. A numerical investigation of the different electric current transition regimes observed during the concentration polarization phenomena in nanochannels is performed. This included a 2D-axisymmetric simulation of the nanofluidic system (reservoir-nanochannel-reservoir). From these simulations, a novel mechanism is discovered that explains that different current transition regimes. This driving mechanism involves the applied electric field penetration while the convective flow mechanism is found to be negligible. This differs with the classical statement that the mixing process with less depleted areas initiated by an electrokinetic vortex instability starts the overlimiting regime. Additionally, the numerical approach allows us to identify new characteristics of the linear-limiting transition such as source-like and saddle-like points of the electric field streamlines. The three voltage-current regimes (linear, limiting and overlimiting) are explained by observing and quantifying changes in electric field, potential, ion concentration and ion concentration gradients within the system.

Recurrent geomagnetic storms and equinoctial ionospheric F-region in the low magnetic latitude: a case study

This paper analyses a case study of 27-day recurrent geomagnetic storms (RGSs) and the ionospheric F-region over Peruvian, Ascension Island, and Port Stanley during vernal equinox in 2006. The RGSs are categorized into High-Intensity Long-Duration Continuous AE Activity (HILDCAA) and non-HILDCAA cases. The solar wind plasma, Ionosonde, and magnetometer data are used. The results reveal that in both cases prompt penetration electric field and disturbance dynamo electric field (DDEF) control the ionospheric plasma and affect night time spread F (SF) that disturbs the HF-radio communications in equatorial and southern crest of equatorial ionization anomaly (EIA). The SF at magnetic equator is delayed, more predominant, and last longer than at the southern EIA. DDEFs and thermospheric winds persist in the recovery phase of storm with stronger ones can inhibit the SF.

Geomagnetic Conjugate Observations of Ionospheric Disturbances in response to North Korea Underground Nuclear Explosion on 3 September 2017

<p><strong>Abstract.</strong> We report observations of ionospheric disturbances in response to North Korea underground nuclear explosion (UNE) on 3 September 2017. By using data from IGS (International GNSS Service) stations and Swarm satellite, geomagnetic conjugate ionospheric disturbances were observed. The observational evidences showed that UNE-generated ionospheric disturbances propagated radially from the UNE epicenter with the velocity of ~<span class="thinspace"></span>280<span class="thinspace"></span>m/s. We propose that the ionospheric disturbances are results of electrodynamic process caused by LAIC (Lithosphere-Atmosphere-Ionosphere Coupling) electric field penetration. LAIC electric field can also be mapped to the conjugate hemispheres along the magnetic field line and consequently cause ionospheric disturbances in conjugate regions. The UNE-generated LAIC electric field penetration plays an important role in the ionospheric disturbances in the region of the nuclear test site nearby and the corresponding geomagnetic conjugate points.</p>

Unusual Generation of Localized EPB in the Dawn Sector Triggered by a Moderate Geomagnetic Storm

AbstractAn interesting piece of observation related to the equatorial plasma bubble (EPB) that is triggered by a geomagnetic storm at dawn sector on 4–5 February 2011 is presented. The storm activity was initiated at 17 UT when interplanetary magnetic field (IMF) Bz turned southward and the Dst index started decreasing (accompanied by AE intensifications) attaining its minimum at −70 nT. The IMF Bz presented large fluctuations marked by southward/northward transitions at slow and rapid rates and eventually returning to normal in the morning of 5 February. Observations from the very high frequency radar located at Gadanki, an off‐equatorial station; an all‐sky imager located at Kolhapur, a low‐latitude station; and an ionosonde at Tirunelveli, an equatorial station, are analyzed to study the impact of this storm on the postmidnight to presunrise equatorial spread F. The results demonstrate that EPB irregularities can be generated by penetration electric field during what can be characterized as a moderate storm event. In contrast to prevailing belief, the present results show that EPB/equatorial spread F can be generated by undershielding electric field in the dawn sector, caused by an unusually delayed polarity reversal of the penetration electric field. The results further reveal oscillatory behavior in the height of F layer topside irregularities in association with IMF Bz oscillations. Observation of radar echoes from nighttime E layer irregularity structures and their Doppler velocities representing the penetration electric field polarity and intensity are also a notable finding of this paper.

Observation of equatorial plasma bubbles by the airglow imager on ISS-IMAP

Using 630 nm airglow data observed by an airglow imager on the International Space Station (ISS), the occurrence of equatorial plasma bubbles (EPBs) is studied. In order to examine the physical mechanisms in the boundary region between the Earth and the outer space, an ionosphere, mesosphere, upper atmosphere, and plasmasphere mapping (IMAP) mission had been conducted onboard the ISS since October 2012. The visible light and infrared spectrum imager (VISI) is utilized in the ISS-IMAP mission for nadir-looking observation of the earth’s atmospheric airglow. In this study, we automatically select EPBs according to the criterion for extracting the tilted dark lines from VISI data. Using the selected events, the dependence of the occurrence rate of EPBs is examined. There is no other report of the occurrence rate of EPBs using downward-looking visible airglow data (630 nm). In this result, the occurrence rate is high at all longitudes in the equinoctial seasons. In the solstice seasons, in contrast, the occurrence rate is very small especially in the Pacific and American sectors. This result is basically consistent with previous studies, e.g., those determined by plasma density data on DMSP satellites.During the June solstice in 2013, EPBs were observed in association with geomagnetic storms that occurred due to a southward turning of the IMF Bz. Using these events, we examined the storm-time features of the occurrence of EPBs in the Pacific-American sectors during the June solstice. In these sectors, where the occurrence rate of EPBs is very small during solstice seasons, some EPBs were observed in the peak and recovery phases of the storms. This result shows that the prompt penetration of electric fields causes the development of EPBs, in the data we analyzed, the geomagnetic storms did not inhibit the generation of EPB in the Pacific–American sectors.