Quantitative forecasting of the 27-day recurrent magnetic activity

Akasofu, S.‐I.; Olmsted, C.; Saito, Takao; Ôki, T.

doi:10.1016/0032-0633(88)90068-2

Cited by 10 publications

(6 citation statements)

References 20 publications

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“…HAFv.2 was calibrated with the same MHD models used to develop ISPM and STOA [ Sun et al , 1985; Akasofu et al , 1988]. We would expect HAFv.2 to perform better at predicting SAT than those two models, because it accounts for the inhomogeneous interplanetary medium through which the shocks propagate and interact.…”

Section: Discussionmentioning

confidence: 99%

Forecasting solar wind structures and shock arrival times using an ensemble of models

Fry¹,

et al. 2003

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[1] Forecasting the time of arrival at Earth of interplanetary shocks following solar metric type II activity is an important first step in the establishment of an operational space weather prediction system. The quality of the forecasts is of utmost importance. The performances of the shock time of arrival (STOA) and interplanetary shock propagation models (ISPM) were previously evaluated by Smith et al. Each model predicts shock arrival time (SAT) at the Earth using real-time metric type II radio frequency drifts and coincident X-ray and optical data for input and L1 satellite observations for verification. Our evaluation of input parameters to the models showed that the accuracy of the solar metric type II radio burst observations as a measure of the initial shock velocity was compromised for those events at greater than 20°solar longitude from central meridian. The HAF model also calculates the interplanetary shock propagation imbedded in a realistic solar wind structure through which the shocks travel and interact. Standard meteorological forecast metrics are used. A variety of statistical comparisons among the three models show them to be practically equivalent in forecasting SAT. Although the HAF kinematic model performance compares favorably with ISPM and STOA, it appears to be no better at predicting SAT than ISPM or STOA. HAFv.2 takes the inhomogeneous, ambient solar wind structure into account and thereby provides a means of sorting event-driven shock arrivals from corotating interaction region (CIR) passage.

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Section: Discussionmentioning

confidence: 99%

Forecasting solar wind structures and shock arrival times using an ensemble of models

Fry¹,

et al. 2003

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“…[2] A quasi-27-day periodicity in various atmospheric, ionospheric, and magnetospheric parameters has previously been reported in numerous studies, some dating to before the space age [e.g., Bartels, 1950;Langehesse, 1953;Chkhetiya, 1975;Akasofu et al, 1988;Hapgood, 1993;Pancheva et al, 1991;Bowman, 1996;Rich et al, 2003;Apostolov et al, 2004;Hocke, 2008, and references therein]. The $27-day solar rotation period is clearly connected with recurrent periodicity in ionospheric disturbances.…”

Section: Introductionmentioning

confidence: 91%

Modification of midlatitude ionospheric parameters in the F2 layer by persistent high‐speed solar wind streams

Denton

Ulich²,

Turunen³

2009

Space Weather

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High‐speed solar wind streams (HSSs) are periods of persistently high solar wind, which emanate from coronal holes and may recur with a frequency related to the solar rotation period of 27 days. On arrival at the Earth's magnetopause, such streams cause a series of events which ultimately lead to changes in the ionospheric F layer. We present a superposed epoch analysis of parameters in the midlatitude F2 layer for a collection of 124 high‐speed solar wind streams which occurred between 1993 and 2006. Clear changes in the critical frequency (foF2), density (NmF2), and height (hmF2) are found to occur after the onset of magnetospheric convection associated with HSS arrival at the Earth's magnetosphere. A fall in foF2 occurs immediately following convection onset accompanied by a sudden decrease in NmF2 and an increase in hmF2. During the events under study, the height of the F2 layer is found to increase by ∼20 km at convection onset. A period of more than 4 days is required for the ionosphere to return to preevent levels. This behavior is explained as the occurrence of ionospheric F region storms following HSS arrival. The results raise the possibility of improved predictions for ionospheric parameters on the basis of upstream solar wind conditions and prior identification of stream interfaces.

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“…If the computed velocity gradients are steep enough., t_he algoritbans allow forward and reverse shocks to be established. We have previously used a 1-D and a 2-D MHD model [Sun et al, 1985;Akasofu et al, 1988] and solar wind data [Olrnsted and to calibrate the earlier version of HAF (version 1) to determine the best set of proxy driver inputs and HAF model internal parameters.…”

Section: Model Improvementsmentioning

confidence: 99%

“…The comparable performance of HAF, STOA, and ISPM is encouraging. HAF (version 1) was calibrated with the same • models used to develop ISPM and STOA [Sun et al, 1985;Akasofu et al, 1988]. Therefore we should not expect HAF (version 1) to perform better than those two models.…”

Section: /05 4/osmentioning

confidence: 99%

Improvements to the HAF solar wind model for space weather predictions

Fry¹,

Sun²,

Deehr³

et al. 2001

J. Geophys. Res.

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172

197

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Abstract. We have assembled and tested, in real time, a space weather modeling system that starts at the Sun and extends to the Earth through a set of coupled, modular components. We describe recent efforts to improve the Hakamada-Akasofu-Fry (HAF) solar wind model that is presently used in our geomagnetic storm prediction system. We also present some results of these improvement efforts. In a related paper, Akasofu

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Quantitative forecasting of the 27-day recurrent magnetic activity

Cited by 10 publications

References 20 publications

Forecasting solar wind structures and shock arrival times using an ensemble of models

Forecasting solar wind structures and shock arrival times using an ensemble of models

Modification of midlatitude ionospheric parameters in the F2 layer by persistent high‐speed solar wind streams

Improvements to the HAF solar wind model for space weather predictions

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