Bibliography

Notice:

Clicking on the title will open a new window with all details of the bibliographic entry.
Clicking on the DOI link will open a new window with the original bibliographic entry from the publisher.
Clicking on a single author will show all publications by the selected author.
Clicking on a single keyword, will show all publications by the selected keyword.

Found 17 entries in the Bibliography.

Showing entries from 1 through 17

2019

An Opposite Response of the Low-Latitude Ionosphere at Asian and American Sectors During Storm Recovery Phases: Drivers From Below or Above

n this study, we focus on the recovery phase of a geomagnetic storm that happened on 6\textendash11 September 2017. The ground-based total electron content data, as well as the F region in situ electron density, measured by the Swarm satellites show an interesting feature, revealing at low and equatorial latitudes on the dayside ionosphere prominent positive and negative responses at the Asian and American longitudinal sectors, respectively. The global distribution of thermospheric O/N₂ ratio measured by global ultraviolet imager on board the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics satellite cannot well explain such longitudinally opposite response of the ionosphere. Comparison between the equatorial electrojet variations from stations at Huancayo in Peru and Davao in the Philippines suggests that the longitudinally opposite ionospheric response should be closely associated with the interplay of E region electrodynamics. By further applying nonmigrating tidal analysis to the ground-based total electron content data, we find that the diurnal tidal components, D0 and DW2, as well as the semidiurnal component SW1, are clearly enhanced over prestorm days and persist into the early recovery phase, indicating the possibility of lower atmospheric forcing contributing to the longitudinally opposite response of the ionosphere on 9\textendash11 September 2017.

Xiong, Chao; Lühr, Hermann; Yamazaki, Yosuke;

Published by: Journal of Geophysical Research: Space Physics Published on: 07/2019

YEAR: 2019 DOI: 10.1029/2019JA026917

2016

High-latitude energy input and its impact on the thermosphere

This paper presents a quantitative assessment of high-latitude energy input and its partitioning in the polar cap by synthesizing various space and ground-based observations during the 17 January 2005 geomagnetic storm. It was found that Joule heating is the primary form of magnetospheric energy input, especially during active times when the hemispheric-integrated Joule heating can be an order of magnitude larger than the hemispheric-integrated auroral power. Most of magnetospheric energy is dissipated in the auroral zone rather than in the polar cap. On average, only about 22\textendash25\% of the total hemispheric energy input is dissipated into the polar cap region bordered by the convection reversal boundary (CRB) and the poleward auroral flux boundary (FXB). The impact of high-latitude energy input was also investigated to unveil the causal relationship between Joule heating and the formation of polar cap mass density anomalies. Our numerical simulation demonstrated that thermosphere dynamics readily redistributes composition, temperature, and mass through upwelling and atmospheric gravity waves. The polar cap mass density anomalies observed by the CHAMP satellite during the storm were largely a result of large-scale atmospheric gravity waves. Therefore, an increase in local thermospheric mass density does not necessarily mean there is direct energy input.

Lu, G.; Richmond, A.; Lühr, H.; Paxton, L.;

Published by: Journal of Geophysical Research: Space Physics Published on: 07/2016

YEAR: 2016 DOI: 10.1002/2015JA022294

Scale analysis of equatorial plasma irregularities derived from Swarm constellation

In this study, we investigated the scale sizes of equatorial plasma irregularities (EPIs) using measurements from the Swarm satellites during its early mission and final constellation

Xiong, Chao; Stolle, Claudia; Lühr, Hermann; Park, Jaeheung; Fejer, Bela; Kervalishvili, Guram;

Published by: Earth, Planets and Space Published on:

YEAR: 2016 DOI: 10.1186/s40623-016-0502-5

2014

Strong ionospheric field-aligned currents for radial interplanetary magnetic fields

The present work has investigated the configuration of field-aligned currents (FACs) during a long period of radial interplanetary magnetic field (IMF) on 19 May 2002 by using high-resolution and precise vector magnetic field measurements of CHAMP satellite. During the interest period IMF B_y and B_z are weakly positive and B_x keeps pointing to the Earth for almost 10 h. The geomagnetic indices Dst is about -40 nT and AE about 100 nT on average. The cross polar cap potential calculated from Assimilative Mapping of Ionospheric Electrodynamics and derived from DMSP observations have average values of 10\textendash20 kV. Obvious hemispheric differences are shown in the configurations of FACs on the dayside and nightside. At the south pole FACs diminish in intensity to magnitudes of about 0.1 μA/m², the plasma convection maintains two-cell flow pattern, and the thermospheric density is quite low. However, there are obvious activities in the northern cusp region. One pair of FACs with a downward leg toward the pole and upward leg on the equatorward side emerge in the northern cusp region, exhibiting opposite polarity to FACs typical for duskward IMF orientation. An obvious sunward plasma flow channel persists during the whole period. These ionospheric features might be manifestations of an efficient magnetic reconnection process occurring in the northern magnetospheric flanks at high latitude. The enhanced ionospheric current systems might deposit large amount of Joule heating into the thermosphere. The air densities in the cusp region get enhanced and subsequently propagate equatorward on the dayside. Although geomagnetic indices during the radial IMF indicate low-level activity, the present study demonstrates that there are prevailing energy inputs from the magnetosphere to both the ionosphere and thermosphere in the northern polar cusp region.

Wang, Hui; Lühr, Hermann; Shue, Jih-Hong; Frey, Harald.; Kervalishvili, Guram; Huang, Tao; Cao, Xue; Pi, Gilbert; Ridley, Aaron;

Published by: Journal of Geophysical Research: Space Physics Published on: 05/2014

YEAR: 2014 DOI: 10.1002/2014JA019951

air upwelling; field-aligned currents; radial interplanetary magnetic field

2013

The Ionospheric Bubble Index deduced from magnetic field and plasma observations onboard Swarm

In the post-sunset tropical ionospheric F-region plasma density often exhibits depletions, which are usually called equatorial plasma bubbles (EPBs). In this paper we give an overview of the Swarm Level 2 Ionospheric Bubble Index (IBI), which is a standard scientific data of the Swarm mission. This product called L2-IBI is generated from magnetic field and plasma observations onboard Swarm, and gives information as to whether a Swarm magnetic field observation is affected by EPBs. We validate the performance of the L2-IBI product by using magnetic field and plasma measurements from the CHAMP satellite, which provided observations similar to those of the Swarm. The L2-IBI product is of interest not only for ionospheric studies, but also for geomagnetic field modeling; modelers can de-select magnetic data which are affected by EPBs or other unphysical artifacts.

Park, J.; Noja, M.; Stolle, C.; Lühr, H.;

Published by: Earth, Planets and Space Published on: 11/2014

YEAR: 2013 DOI: 10.5047/eps.2013.08.005

Equatorial ionosphere; Plasma irregularity; topside ionosphere

Nonmigrating tidal signatures in the magnitude and the inter-hemispheric asymmetry of the equatorial ionization anomaly

Based on nine years of observations from the satellites CHAMP and GRACE the tidal signatures in the magnitude and the inter-hemisphere asymmetry of the equatorial ionization anomaly (EIA) have been investigated in this study. The EIA magnitude parameters show longitudinal wavenumber 4 and 3 (WN4/WN3) patterns during the months around August and December, respectively, while for different EIA parameters the contributions of the various tidal parameters are different. For the crest- to-trough ratio (CTR) the dominating nonmigrating tidal component contributing to WN4 is DE3 during the months around August, while during the months around December solstice the stationary planetary wave, SPW3, takes a comparable role to DE2 in contributing to WN3. For the apex height index (ApexHC) of the EIA fluxtube the stationary planetary waves, SPW4/SPW3, exceed the amplitudes of DE3/DE2 taking the leading role in causing the longitudinal WN4/WN3 patterns. During the\ months around December solstice the SW3 tide is prominent in both CTR and ApexHC. SW3 shows a strong dependence on the solar flux level, while it is hardly dependent on magnetic activity. For the EIA interhemispheric asymmetry only WN1 and WN2 longitudinal patterns can be seen. During June solstice months the pattern can be explained by stationary planetary waves SPW1 and SPW2. Conversely, around December solstice months longitudinal features exhibit some local time evolution,\ in particular the diurnal nonmigrating tide D0 takes the leading role.

Xiong, C.; Lühr, H.;

Published by: Annales Geophysicae Published on: 01/2013

YEAR: 2013 DOI: 10.5194/angeo-31-1115-2013

Atmospheric dynamics; Equatorial ionosphere; Ionosphere; ionosphere\textendashatmosphere interactions. Meteorology

Determining the equatorward and poleward boundaries of the auroral oval from CHAMP field-aligned currents signatures

IRI peak E-region electron density with assimilated auroral NmE from GUVI auroral model.

Xiong, Chao; Lühr, Hermann; Ritter, Patricia;

Published by: Published on:

YEAR: 2013 DOI:

The Ionospheric Bubble Index deduced from magnetic field and plasma observations onboard Swarm

In the post-sunset tropical ionospheric F-region plasma density often exhibits depletions, which are usually called equatorial plasma bubbles (EPBs). In this paper we give an overview

Park, Jaeheung; Noja, Max; Stolle, Claudia; Lühr, Hermann;

Published by: Earth, Planets and Space Published on:

YEAR: 2013 DOI: https://doi.org/10.5047/eps.2013.08.005

High-latitude Thermospheric Density and Wind Dependence on Solar and Magnetic Activity

Processes in the high-latitude thermosphere are strongly controlled by the activity of the sun and by the geomagnetic field geometry. The CHAMP satellite, with its sensitive tri-axial accelerometer, provided detailed information about thermospheric dynamics over its mission life-time (2000\textendash2010), thus contributing significantly to the CAWSES (Climate And Weather of the Sun-Earth System) programme. In this chapter, studies on thermospheric winds and density anomalies at high magnetic latitudes are presented. Thermospheric winds above the poles are directed predominantly from day to night side. Observations, however, reveal a distinct difference between winds on the dawn and dusk sides at auroral latitudes. While on the dawn side fast zonal winds towards night are prevailing, an anti-cyclonic vortex is formed on the dusk side. For the explanation of these local time dependent features various thermodynamic and electrodynamic influences have to be considered. As an example for mass density variation the cusp-related density anomaly is studied. The amplitude of this prominent local peak in mass density is influenced by the level of solar flux (F10.7) and by the solar wind input into the magnetosphere as quantified by the electric field caused by reconnection. A prerequisite for the appearance of density anomalies is the presence of soft-energy particle precipitation. By combining CHAMP and EISCAT measurements, it has been shown that Joule heating, fuelled predominantly by small-scale field-aligned currents (FACs), causes a strong increase in temperature at altitudes below 200 km. As a consequence molecular-rich air is up-welling. A density anomaly is recorded at 400 km altitude. Combining different observations and numerical model results provides a plausible chain of processes leading to the observed cusp-related density anomaly.

Lühr, Hermann; Marker, Stefanie;

Published by: Published on:

YEAR: 2013 DOI: 10.1007/978-94-007-4348-9_11

2012

A long-lived band of plasma density enhancement at mid-latitudes during the 2003 Halloween magnetic storm

Park, Jaeheung; Lühra, Hermann; Jakowski, Norbert; Gerzen, Tatjana; Kil, Hyosub; Jee, Geonhwa; Xiong, Chao; Min, Kyoung; Noja, Max;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on: Jan-05-2012

YEAR: 2012 DOI: 10.1016/j.jastp.2012.03.009

2010

Neutral density depletions associated with equatorial plasma bubbles as observed by the CHAMP satellite

Using CHAMP observations from 2002 to 2005 we investigate neutral density depletions (NDDs) associated with equatorial plasma bubbles (EPBs). The seasonal–longitudinal distribution of NDDs generally follows that of EPBs. However, there are several important differences between them. The maximum NDD occurrence rate is much smaller than the maximum EPB occurrence. NDDs occur at latitudes north and south of the dip equator with an offset of about 15∘, which is collocated with the Appleton anomaly peaks and slightly poleward of EPB occurrence maxima. The NDD occurrence maximizes around 21 LT, and has nearly died out after 23 LT. Meanwhile, the EPB occurrence shows a broad maximum between 20 and 24 LT. NDD distribution deviates slightly from that of EPBs shifted toward the region of high ion–neutral interaction. Based on our statistical results, as well as on some physics-based calculations, we suggest that an enhanced friction between ions and neutrals is needed for the NDD generation.

Park, Jaeheung; Lühr, Hermann; Min, Kyoung;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics Published on:

YEAR: 2010 DOI: https://doi.org/10.1016/j.jastp.2009.11.003

ionospheric irregularities; Equatorial ionosphere; thermospheric dynamics; ionosphere/atmosphere interactions

2009

The characteristics of field-aligned currents associated with equatorial plasma bubbles as observed by the CHAMP satellite

Park, J.; Lühr, H.; Stolle, C.; Rother, M.; Min, K.; Michaelis, I.;

Published by: Annales Geophysicae Published on: Jan-01-2009

YEAR: 2009 DOI: 10.5194/angeo-27-2685-2009

The 27-day modulation of the low-latitude ionosphere during a solar maximum

Min, Kyoung; Park, Jaeheung; Kim, Heejun; Kim, Vitaly; Kil, Hyosub; Lee, Jaejin; Rentz, Stefanie; Lühr, Hermann; Paxton, Larry;

Published by: Journal of Geophysical Research: Space Physics Published on: