Bibliography

Hemispheric distributions and interannual variability of NO _y produced by energetic particle precipitation in 2002-2012

We investigate the interannual variability and hemispheric differences of reactive odd nitrogen produced by energetic particle precipitation (EPP-NO_y) and transported into the stratosphere and lower mesosphere during polar winters in 2002\textendash2012. For this purpose, EPP-NO_y amounts derived from observations of the Michelson Interferometer for Passive Atmospheric Sounding by means of a tracer correlation method have been used. Southern hemispheric (SH) seasonal maximum EPP-NO_y amounts transported below the 0.02 hPa level range from 0.5GM to 2.5GM in the 2009 and 2003 winters, respectively. Northern hemispheric (NH) amounts were typically 2\textendash5 times smaller, with the exception of the 2003/2004 winter. This interhemispheric asymmetry is primarily caused by a reduction of the mesospheric descent rates in NH midwinter, as opposed to the SH. Hemispherically integrated NO_y fluxes through given pressure levels reach up to 0.07GM/day at 0.1 hPa. A multilinear regression of the EPP-NO_y evolution to the A_p index of the preceding months indicates that a large fraction of the SH interannual variability of EPP-NO_y (excluding direct contributions by solar protons) can be linked to geomagnetic activity variations. This relationship holds throughout the winter and at all vertical levels where EPP-NO_y is present. In the NH, a similar correlation is found until midwinter, however, breaking down afterward above 2 hPa in years with elevated stratopause occurrence. As an exception, EPP-NO_y amounts in the Arctic winter 2004/2005 were much higher than in other NH winters with similar geomagnetic activity. We attribute this behavior to the unusually stable polar vortex in that winter, otherwise typical for the SH.

Funke, B.; opez-Puertas, M.; Holt, L.; Randall, C.; Stiller, G.; von Clarmann, T.;

Published by: Journal of Geophysical Research: Atmospheres      Published on: 11/2014

YEAR: 2014     DOI: 10.1002/2014JD022423

Long-term ionospheric cooling: Dependency on local time, season, solar activity, and geomagnetic activity

Ionospheric ion temperature Ti is an excellent approximation to neutral temperature Tn in the thermosphere, especially for altitudes below 300 km. This analysis of long-term Ti trends in the F region over different local times is based on a database of incoherent scatter radar (ISR) observations spanning more than three solar cycles during 1968\textendash2006 at Millstone Hill and represents an extended effort to a prior study focusing on noon-time only. This study provides important information for understanding the difference between the ISR and other results. A gross average of the Ti trend at heights of Ti \~ Tn (200\textendash350 km) is \~ -4 K/decade, a cooling trend close to the Tn estimation based on the satellite neutral density data. However, there exists considerable variability in the cooling: it is strong during the day and very weak during the night with a large apparent warming at low altitudes (200\textendash350 km); it is strong at solar minimum for both daytime and nighttime. The strongest cooling for altitudes below 375 km occurs around 90\textendash120 solar flux units of the 10.7 cm solar flux, not at the lowest solar flux. There appears more cooling toward high magnetic activity, but this dependency is very weak. No consistent and substantial seasonal dependency across different heights was found. We speculate that a fraction of the observed cooling trend may be contributed by a gradual shifting away from the sub-auroral region at Millstone Hill, as part of the secular change in the Earth\textquoterights magnetic field. In this 39 year long series of data record, two anomalous Ti drops were noticed, and we speculate on their connection to volcano eruptions in 1982 and 1991.

Zhang, Shun-Rong; Holt, John;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2013

YEAR: 2013     DOI: 10.1002/jgra.50306

global change; incoherent scatter radar; ionospheric temperature; long-term trend; Millstone Hill

Measured and modeled ionospheric densities, temperatures, and winds during the international polar year

Richards, PG; Nicolls, MJ; Heinselman, CJ; Sojka, JJ; Holt, JM; Meier, RR;

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

YEAR: 2009     DOI:

Variations of topside ionospheric scale heights over Millstone Hill during the 30-day incoherent scatter radar experiment

A 30-day incoherent scatter radar (ISR) experiment was conducted at Millstone Hill (288.5 E, 42.6 N) from 4 October to 4 November 2002. The altitude profiles of electron density N e

Liu, L; Wan, W; Zhang, M-L; Ning, B; Zhang, S-R; Holt, JM;

Published by:       Published on:

YEAR: 2007     DOI: 10.5194/angeo-25-2019-2007

October 2002 30-day incoherent scatter radar experiments at Millstone Hill and Svalbard and simultaneous GUVI/TIMED observations

A long-duration incoherent scatter radar (ISR) experiment was conducted at Millstone Hill and Svalbard from October 4\textendashNovember 4, 2002. Along with the simultaneous GUVI/TIMED neutral composition measurements, this 30-day run enabled us to study a number of thermosphere-ionosphere-magnetosphere phenomena. This paper focuses on the day-to-day variability and quasiperiodic oscillation of the ionosphere. The day-to-day variability under quiet magnetic conditions in electron density Ne, ion temperature Ti and electron temperature Te, respectively, changed with local time and height, with the largest variability in Ne and the smallest in Ti. Midnight through dawn was the period of largest variability. Quasiperiodic Ne oscillations were present with periods \>1 day. Some of these oscillations were correlated with changes in the neutral composition originating from geomagnetic activity, which altered the global atmospheric circulation as a result of high latitude heating processes as indicated in Svalbard ion temperature enhancements. However, the wave-type oscillation of Ne exhibits a downward phase progression which persists up to 600 km and prevails until a large storm appears to impose an upward phase progression.

Zhang, Shun-Rong; Holt, John; Erickson, Phil; Lind, Frank; Foster, John; van Eyken, Anthony; Zhang, Yongliang; Paxton, Larry; Rideout, William; Goncharenko, Larisa; Campbell, Glenn;

Published by: Geophysical Research Letters      Published on: 01/2005

YEAR: 2005     DOI: 10.1029/2004GL020732

Space Sciences-L01108 October 2002 30-day incoherent scatter radar experiments at Millstone Hill and Svalbard and simultaneous GUVI/TIMED observations (DOI 10.1029/2004GL020732)

Zhang, Shun-Rong; Holt, John; Erickson, Phil; Lind, Frank; Foster, John; van Eyken, Anthony; Zhang, Yongliang; Paxton, Larry; Rideout, William; Goncharenko, Larisa; , others;

Published by: Geophysical Research Letters      Published on:

YEAR: 2005     DOI: