The thermospheric semiannual density response to solar EUV heating

Bowman, Bruce R.; Tobiska, W. Kent; Kendra, M. J.

doi:10.1016/j.jastp.2008.04.020

Cited by 41 publications

(54 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is well known from studies based on satellite drag measurements that the upper thermospheric density exhibits annual and semiannual variations. The thermospheric density is at a maximum during the equinox months with a primary minimum in July and secondary minimum in January [e.g., Paetzold and Zschörner, 1961;Qian et al 2009;Lei et al, 2012b], and the amplitude difference between maximum and minimum can depend on both height and solar EUV flux [Bowman et al 2008]. Although we do not endeavor to discuss the mechanisms for the seasonal variations, we note that our results for 350 km show that the density is indeed maximum in the equinox months (8.92Â10 13 m -3 ), and lowest in summer (6.13Â10 13 m -3 ) with the secondary minimum in winter (7.61Â10 13 m -3 ).…”

Section: Discussionmentioning

confidence: 99%

Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

et al. 2013

View full text Add to dashboard Cite

[1] Coupling between the ionized and neutral atmosphere through particle collisions allows an indirect study of the neutral atmosphere through measurements of ionospheric plasma parameters. We estimate the neutral density of the upper thermosphere above~250 km with the European Incoherent Scatter Svalbard Radar (ESR) using the year-long operations of the International Polar Year from March 2007 to February 2008. The simplified momentum equation for atomic oxygen ions is used for field-aligned motion in the steady state, taking into account the opposing forces of plasma pressure gradients and gravity only. This restricts the technique to quiet geomagnetic periods, which applies to most of the International Polar Year during the recent very quiet solar minimum. The method works best in the height rangẽ 300-400 km where our assumptions are satisfied. Differences between Mass Spectrometer and Incoherent Scatter and ESR estimates are found to vary with altitude, season, and magnetic disturbance, with the largest discrepancies during the winter months. A total of 9 out of 10 in situ passes by the CHAMP satellite above Svalbard at 350 km altitude agree with the ESR neutral density estimates to within the error bars of the measurements during quiet geomagnetic periods.

show abstract

Section: Discussionmentioning

confidence: 99%

Thermospheric atomic oxygen density estimates using the EISCAT Svalbard Radar

et al. 2013

View full text Add to dashboard Cite

show abstract

“…The solar EUV/FUV radiation is absorbed in the terrestrial atmosphere at ~50-200 km altitude (Bowman et al 2008) and affects the density and temperature of ionospheric ions. The long-term variations of EUV/FUV may control the supply of ionospheric ions into the space plasma and change the ion composition.…”

Section: Mg II Indexmentioning

confidence: 99%

Long-term variations in the plasma sheet ion composition and substorm occurrence over 23 years

Nosé

2016

Geosci. Lett.

View full text Add to dashboard Cite

The Geotail satellite has been operating for almost two solar cycles (~23 years) since its launch in July 1992. The satellite carries the energetic particle and ion composition (EPIC) instrument that measures the energetic ion flux (9.4-212 keV/e) and enables the investigation of long-term variations of the ion composition in the plasma sheet for solar cycles 22-24. From the statistical analysis of the EPIC data, we find that (1) the plasma ion mass (M) is approximately 1.1 amu during the solar minimum, whereas it increases to 1.5-2.7 amu during the solar maximum; (2) the increases in M seem to have two components: a raising of the baseline levels (~1.5 amu) and a large transient enhancement (~1.8-2.7 amu); (3) the baseline level change of M correlates well with the Mg II index, which is a good proxy for the solar extreme ultraviolet (EUV) or far ultraviolet (FUV) irradiance; and (4) the large transient enhancement of M is caused by strong magnetic storms. We also study the long-term variations of substorm occurrences in 1992-2015 that are evaluated with the number of Pi2 pulsations detected at the Kakioka observatory. The results suggest no clear correlation between the substorm occurrence and the Mg II index. Instead, when the substorms are classified into externally triggered events and non-triggered events, the number of the non-triggered events and the Mg II index are negatively correlated. We interpret these results that the increase in the solar EUV/FUV radiation enhances the supply of ionospheric ions (He + and O + ions) into the plasma sheet to increase M, and the large M may suppress spontaneous plasma instabilities initiating substorms and decrease the number of the non-triggered substorms. The present analysis using the unprecedentedly long-term dataset covering ~23 years provides additional observational evidence that heavy ions work to prevent the occurrence of substorms.

show abstract

“…Particularly important are the hysteresis effects where the effects of the same event may depend on the history of events which took place before it. Some atmospheric models in use include that of Picone et al (2002), Bruinsma et al (2003), Bowman et al (2008), Emmert andPicone, 2010, Liu et al (2013) and others. In our work, atmospheric density profiles are obtained from the NRLMSISE-00 empirical atmospheric model.…”

Section: Upper Atmospheric Density Profilementioning

confidence: 99%