Causes of low thermospheric density during the 2007-2009 solar minimum

Solomon, Stanley C.; Qian, Liying; Didkovsky, L. V.; Viereck, R. A.; Woods, Thomas N.

doi:10.1029/2011ja016508

Cited by 124 publications

(170 citation statements)

References 53 publications

(73 reference statements)

Supporting

Mentioning

159

Contrasting

Order By: Relevance

“…The actual UV flux is overestimated with the F10.7 proxy during the last solar minimum, and consequently models overestimate density (Solomon et al 2010(Solomon et al , 2011. Since this effect is also seen DTM2013, F30 apparently also overestimated the UV flux during the last minimum, but less.…”

Section: Overall Relative Model Precisionmentioning

confidence: 89%

The DTM-2013 thermosphere model

Bruinsma¹

2015

J. Space Weather Space Clim.

148

102

View full text Add to dashboard Cite

Aims -The Drag Temperature Model (DTM) is a semi-empirical model describing the temperature, density, and composition of the Earth's thermosphere. DTM2013 was developed in the framework of the Advanced Thermosphere Modelling and Orbit Prediction project (ATMOP). It is evaluated and compared with DTM2009, the pre-ATMOP benchmark, and the Committe on Space Research (COSPAR) reference model for atmospheric drag JB2008. Methods -The total density data used in this study, including the high-resolution CHAMP, GRACE and GOCE data, cover the 200-900 km altitude range and all solar activities. DTM2013 was constructed with the data assimilated in DTM2009, but with more GRACE data, and low-altitude GOCE data in particular. The solar activity proxy, F10.7 in DTM2009, has been replaced with F30. The bias and precision of the models is evaluated by comparing to the observations according to a metric, which consists of computing mean, RMS, and correlation. Secondly, the residuals are binned, which procedure aids in revealing specific model errors.Results -This evaluation shows that DTM2013 is the least biased and most precise model for the data that were assimilated.Comparison to independent density data shows that it is also the most accurate model overall. It is a significant improvement over DTM2009 under all conditions and at all altitudes, but the largest improvements are obtained at low altitude thanks to GOCE data. The precision of JB2008 decreases with altitude, which is due to its modeling of variations in local solar time and seasons in particular of the exospheric temperature rather than modeling these variations for the individual constituents.

show abstract

Section: Overall Relative Model Precisionmentioning

confidence: 89%

The DTM-2013 thermosphere model

Bruinsma¹

2015

J. Space Weather Space Clim.

148

102

View full text Add to dashboard Cite

show abstract

“…We reexamine the importance of temperature effects on the winter anomaly in this paper using the formulation described by Roble [1995] for the reaction of O + with N 2 3. Results [Solomon et al, 2011]. Direct EUV measurements from Solar Extreme ultraviolet Experiment [Woods et al, 1994] indicate that EUV radiation was even lower in these 2 years.…”

Section: The Reduced Continuity Equationmentioning

confidence: 99%

On the solar cycle variation of the winter anomaly

et al. 2014

View full text Add to dashboard Cite

Constellation Observing System for Meteorology, Ionosphere and Climate, Ionosonde, and Global Ultraviolet Imager data have been used to investigate the solar cycle changes in the winter anomaly (the winter anomaly is defined as the enhancement of the F 2 peak electron density in the winter hemisphere over that in the summer hemisphere) in the last solar cycle. There is no winter anomaly in solar minimum, and an enhancement of about 50% in winter over summer ones on the same day of the year at solar maximum. This solar cycle variation in the winter anomaly is primarily due to greater winter to summer differences of [O]/[N 2 ] in solar maximum than in solar minimum, with a secondary contribution from the effects of temperature on the recombination coefficient between O + and the molecular neutral gas. The greater winter increases in electron density in the Northern Hemisphere than in the Southern Hemisphere appear to be related to the greater annual variation of [O]/[N 2 ] in the north than in the south.

show abstract

“…In response to those low fluxes, the density of the Earth thermosphere dropped 20% lower than earlier minima Solomon et al 2010Solomon et al , 2011, while in the ionosphere, the f 0 F 2 index was depressed by 10% (Coley et al 2010;Chen et al 2011;Lean et al 2011b;Liu et al 2011b).…”

Section: Introductionmentioning

confidence: 99%

“…Exceptionally low levels of the UV irradiance were measured by several instruments. Relative to the solar cycle 22-23 minimum, the SEM UV fluxes were 10% lower and the MgII core-to-wing ratio, a key proxy for the chromosphere and low corona, was 10% lower, an unprecedented level Solomon et al 2010Solomon et al , 2011Woods 2010b;Lean et al 2011a). Tapping & Valdés (2011) also show a drop of the minimum F 10.7 radio flux below the average of the four previous minima, but it is comparatively small (3%).…”

Section: Introductionmentioning

confidence: 99%

Are the sunspots really vanishing?

Clette

Lefèvre

2012

J. Space Weather Space Clim.

View full text Add to dashboard Cite

Context:The elapsed solar cycle (23) ended with an exceptionally long period of low activity and with unprecedented low levels for various series of solar irradiance and particle flux measurements. This unpredicted evolution of solar activity raised multiple questions about a future decline of the solar cycles and launched a quest for precursor signs of this possible deep solar transition over the last decade. Aim: We present here a review and overall interpretation of most current diagnostics of solar cycle 23, including the recent disagreements that appeared among solar reference indices and standard solar-based geo-indices, the indication of a changed pattern of internal torsional waves (helioseismology) or the announced fading and magnetic weakening of sunspots. Methods: Based on a statistical analysis of detailed sunspot properties over the last 24 years, we complete the picture with new evidence of a strong global deficit of the smallest sunspots starting around 2000, in order to answer the question: are all sunspots about to disappear? Results: This global scale-dependent change in sunspot properties is confirmed to be real and not due to uncontrolled biases in some of the indices. It can also explain the recent discrepancies between solar indices by their different sensitivities to small and weak magnetic elements (small spots). The International Sunspot Index R i , based on unweighted sunspot counts, proved to be particularly sensitive to this particular small-scale solar evolution. Conclusions: Our results and interpretation show the necessity to look backwards in time, more than 80 years ago. Indeed, the Sun seems to be actually returning to a past and hardly explored activity regime ending before the 1955-1995 Grand Maximum, which probably biased our current space-age view of solar activity.

show abstract

Causes of low thermospheric density during the 2007-2009 solar minimum

Cited by 124 publications

References 53 publications

The DTM-2013 thermosphere model

The DTM-2013 thermosphere model

On the solar cycle variation of the winter anomaly

Are the sunspots really vanishing?

Contact Info

Product

Resources

About