Unreliable IAGA-endorsed Polar Cap (PC) index series and a different approach

2020 ◽  
Author(s):  
Peter Stauning
Keyword(s):  
Solar Wind ◽  
Real Time ◽  
Space Weather ◽  
Magnetic Data ◽  
Reference Level ◽  
Sector Structure ◽  
Reference Levels ◽  
Polar Cap ◽  
The Real ◽  
Critical Note

<p>The Polar Cap (PC) indices are derived from the magnetic variations generated by the transpolar convection of magnetospheric plasma and embedded magnetic fields driven by the interaction with the solar wind. The PC indices are potentially very useful for Space Weather monitoring and forecasts and for related research. However, the PC index series in the near-real time and final versions endorsed by the International Association for Geomagnetism and Aeronomy (IAGA) have been proven unreliable (Stauning, 2013, 2015, 2018a,b,c, 2020). Both versions include solar wind sector (SWS) effects in the calculation of the reference levels from which magnetic disturbances are measured. The SWS effects are caused by current systems in the dayside Cusp region related to the Y-component, BY, of the Interplanetary Magnetic Field (IMF). However, the IAGA-endorsed handling of SWS effects may generate unfounded PC index changes of up to 3 mV/m at the nightside away from the Cusp. For the real-time PCN and PCS indices, their cubic spline-based reference level construction may cause additional unjustified index excursions of more than 3 mV/m with respect to the corresponding final index values. Noting that PC index values above 2 mV/m indicate geomagnetic storm conditions, such unjustified contributions are considered to invalidate the IAGA-endorsed PC index series. The presentation shall include a description of alternative derivation methods shown to provide more consistent index reference levels for both final and real-time PC indices, to reduce their unfounded excursions, and to significantly increase their reliability (Stauning, 2016, 2018b,c).</p><p><strong>References. </strong>Stauning, P. (2020): The Polar Cap (PC) index: invalid index series and a different approach. Space Weather, 2020SW002442 (submitted).</p><p>Stauning, P. (2013). Comments on quiet daily variation derivation in “Identification of the IMF sector structure in near-real time by ground magnetic data” by Janzhura and Troshichev (2011). Annales Geophysicae, 31, 1221-1225. https://doi.org/10.5194/angeo-31-1221-2013 .</p><p>Stauning, P. (2015). A critical note on the IAGA-endorsed Polar Cap index procedure: effects of solar wind sector structure and reverse polar convection. Annales Geophysicae, 33<strong>, </strong>1443-1455. https://doi.org/10.5194/angeo-33-1443-2015 .</p><p>Stauning, P. (2016). The Polar Cap (PC) Index.: Derivation Procedures and Quality Control. DMI Scientific Report SR-16-22. Available at: https://www.dmi.dk/fileadmin/user_upload/Rapporter/TR/2016/SR-16-22-PCindex.pdf .</p><p>Stauning, P. (2018a). A critical note on the IAGA-endorsed Polar Cap (PC) indices: excessive excursions in the real-time index values. Annales Geophysicae, 36, 621–631. https://doi.org/10.5194/angeo-36-621-2018 .</p><p>Stauning, P. (2018b): Multi-station basis for Polar Cap (PC) indices: ensuring credibility and operational reliability. Journal of Space Weather and Space Climate, 8, A07. https://doi.org/10.1051/swsc/2017036 .</p><p>Stauning, P. (2018c). Reliable Polar Cap (PC) indices for space weather monitoring and forecast</p>

scholarly journals Comment on “Identification of the IMF sector structure in near-real time by ground magnetic data” by Janzhura and Troshichev (2011)

2021 ◽  
Vol 39 (2) ◽  
pp. 369-377
Author(s):  
Peter Stauning
Keyword(s):  
Solar Wind ◽  
Real Time ◽  
International Association ◽  
Magnetic Data ◽  
Reference Level ◽  
Sector Structure ◽  
Polar Cap ◽  
Ground Magnetic ◽  
The Imf

Abstract. The only published description of the solar wind sector (SS) term used for the reference level in the post-event and real-time derivation of the Polar Cap (PC) indices, PCN (Polar Cap North) and PCS (Polar Cap South), in the version endorsed by the International Association for Geomagnetism and Aeronomy (IAGA) is found in the commented publication, Janzhura and Troshichev: Identification of the IMF sector structure in near-real time by ground magnetic data, Annales Geophysicae, 29, 1491–1500, 2011. Actually, the publication has served as a basis for the index endorsement by IAGA in 2013. However, neither the illustrations nor the results presented there have been derived by the specified near real-time method. Figures 1, 6, 7, and 8 display values derived by post-event calculations based on daily medians smoothed over 7 d centred on the day of interest. Figures 2, 3, and 4 display observed values smoothed over 7 d, while the remaining Fig. 5 displays averages over 4 months. In summary, there are strong disagreements between indications in the title, abstract, and statements in the text compared to the actual results and their illustrations.

scholarly journals Comment on Identification of the IMF sector structure in near-real time by ground magnetic data by Janzhura and Troshichev (2011)

2020 ◽  
Author(s):  
Peter Stauning
Keyword(s):  
Solar Wind ◽  
Real Time ◽  
International Association ◽  
Magnetic Data ◽  
Reference Level ◽  
Sector Structure ◽  
Polar Cap ◽  
Ground Magnetic ◽  
The Imf

Abstract. The only published description of the solar wind sector (SS) term used for the reference level in the post-event and real-time derivation of the Polar Cap (PC) indices, PCN (North) and PCS (South), in the version endorsed by the International Association for Geomagnetism and Aeronomy (IAGA) is found in the commented publication, Janzhura and Troshichev (2011): Identification of the IMF sector structure in near-real time by ground magnetic data, Annales Geophysicae, 29, 1491–1500. Actually, the publication has served as basis for the index endorsement by IAGA in 2013. However, neither the illustrations nor the results presented there have been derived by the specified near-real time method. Figs. 1, 6, 7, and 8 display values derived by post-event calculations based on daily medians smoothed over 7 days centred on the day of interest. Figs. 2, 3, and 4 display observed values smoothed over 7 days, while the remaining Fig. 5 displays averages over 4 months. In summary, there are strong disagreements between indications in the title, abstract, and statements in the text compared to the actual results and their illustrations.

scholarly journals Comments on quiet daily variation derivation in "Identification of the IMF sector structure in near-real time by ground magnetic data" by Janzhura and Troshichev (2011)

2013 ◽  
Vol 31 (7) ◽  
pp. 1221-1225 ◽  
Author(s):  
P. Stauning
Keyword(s):  
Solar Wind ◽  
Real Time ◽  
Daily Variation ◽  
Magnetic Data ◽  
Sector Structure ◽  
Polar Cap ◽  
Ground Magnetic ◽  
The Imf

Abstract. The description presented in the paper of the relations of the solar wind sector structure to the derivation of the quiet daily variation (QDC) in polar magnetic recordings used for calculation of polar cap (PC) indices is found to be unclear and not properly justified. The presented example on inclusion of a solar sector term in an actual QDC series is found to be questionable even on the authors' premises.

scholarly journals Reliable real-time Polar Cap (PC) indices for space weather monitoring and forecasts

2018 ◽  
Vol 8 ◽  
pp. A49 ◽  
Author(s):  
Peter Stauning
Keyword(s):  
Real Time ◽  
Space Weather ◽  
International Association ◽  
Magnetic Activity ◽  
Magnetic Data ◽  
Polar Cap ◽  
International Scientific Community ◽  
Order Of Magnitude ◽  
General Basis ◽  
Index Calculation

The Polar Cap (PC) indices were approved by the International Association for Geomagnetism and Aeromony (IAGA) by Resolution No. 3 (2013) noting that “IAGA … recommends use of the PC index by the international scientific community in its near-real time and definitive forms”. PC indices were made available in 2014 at the web portal http://pcindex.org holding near-real time as well as final index values. The near-real time PC index values are not permanently available. However, analyses of indices on basis of occasional downloads have detected differences between near-real time and final PC indices of up to 3.65 mV/m (Stauning, 2018b, Ann Geophys, 36, 621–631). At such differences, one or the other index may indicate (or hide) strong geomagnetic activity without justification in the actual conditions. The present work has disclosed the cause of observed large differences between real-time and final PC index values in the IAGA-endorsed versions. In addition, anticipated differences are derived on a general basis from the available basic magnetic data by using the index calculation procedures and calibration constants provided by the PC index suppliers. It is shown that corresponding or even larger anomalies are expected to be common during moderate to strong magnetic activity where the near-real time PC indices might otherwise prove very useful for space weather monitoring, e.g., for power grid protection. An alternative real-time PC index derivation scheme described here reduces the excessive differences between real-time and final PC index values by an order of magnitude.

scholarly journals A critical note on the IAGA-endorsed Polar Cap (PC) indices: excessive excursions in the real-time index values

2018 ◽  
Vol 36 (2) ◽  
pp. 621-631 ◽  
Author(s):  
Peter Stauning
Keyword(s):  
Real Time ◽  
Present Note ◽  
International Association ◽  
Polar Cap ◽  
Storm Activity ◽  
Strong Magnetic Storm ◽  
The Real ◽  
Critical Note ◽  
Derivation Procedure ◽  
Modelling And Forecasting

Abstract. The Polar Cap (PC) indices were approved by the International Association for Geomagnetism and Aeronomy (IAGA) in 2013 and made available at the web portal http://pcindex.org holding prompt (real-time) as well as archival index values. The present note provides the first reported examination of the validity of the IAGA-endorsed method to generate real-time PC index values. It is demonstrated that features of the derivation procedure defined by Janzhura and Troshichev (2011) may cause considerable excursions in the real-time PC index values compared to the final index values. In examples based on occasional downloads of index values, the differences between real-time and final values of PC indices were found to exceed 3 mV m−1, which is a magnitude level that may indicate (or hide) strong magnetic storm activity. Keywords. Magnetospheric physics (solar wind–magnetosphere interactions; polar cap phenomena) – ionosphere (modelling and forecasting)

scholarly journals A critical note on the IAGA-endorsed Polar Cap index procedure: effects of solar wind sector structure and reverse polar convection

2015 ◽  
Vol 33 (11) ◽  
pp. 1443-1455 ◽  
Author(s):  
P. Stauning
Keyword(s):  
Solar Wind ◽  
International Association ◽  
Sector Structure ◽  
Polar Cap ◽  
Azimuthal Component ◽  
Index Procedure ◽  
Polar Caps ◽  
Critical Note ◽  
Quiet Day ◽  
Derivation Procedure

Abstract. The International Association of Geomagnetism and Aeronomy (IAGA) has recently endorsed a new Polar Cap (PC) index version to supersede the previous seven different versions of the PCN (North) index and the five different PCS (South) index versions. However, the new PC index has some adverse features which should be known and taken into account by users of the index. It uses in its derivation procedure an "effective" quiet day level (QDC) composed of a "basic" QDC and an added solar wind sector term related to the azimuthal component (By) of the interplanetary magnetic field (IMF). The added IMF By-related terms may introduce unjustified contributions to the PC index of more than 2 index units (mV m−1). Furthermore, cases of reverse convection during strong northward IMF Bz (NBZ) conditions included in the database for calculation of index coefficients can cause unjustified index enhancements of 0.5–1 mV m−1 during calm conditions, reduction of index values by more than 20 % during disturbed conditions, and inconsistencies between index coefficients and index values for the northern and southern polar caps. The aim here is to specify these adverse features and quantify their effects, and to suggest alternative steps for future modifications of the index procedure.

scholarly journals Identification of the IMF sector structure in near-real time by ground magnetic data

2011 ◽  
Vol 29 (8) ◽  
pp. 1491-1500 ◽  
Author(s):  
A. S. Janzhura ◽  
O. A. Troshichev
Keyword(s):  
Real Time ◽  
Magnetic Activity ◽  
Magnetic Data ◽  
Sector Structure ◽  
Polar Cap ◽  
Simple Method ◽  
Interpolation Procedure ◽  
Time Regime ◽  
Ground Magnetic ◽  
Good Agreement

Abstract. A method is proposed to determine in near-real time the interplanetary magnetic field (IMF) sector structure (SS) effect on geomagnetic data from polar cap stations. To separate the SS effect, whose polarity is invariant within an interval from some days to 2 weeks, from the disturbed solar wind effects with periodicity from minutes to hours, the daily median values of geomagnetic H (or D) component are estimated. Then the median values for 9 days preceding the current day are subjected to 3-days running averages and the interpolation procedure is applied to these smoothed averages. Comparisons of the sector structure reconstructed from the ground magnetic data with the actual variations of the GSM IMF By component measured onboard the ACE spacecraft in the summer months of 1990 and 2001 demonstrate their good agreement with coefficient of correlation R=0.96–0.97 for the H-component and R=0.93–0.95 for the D-component. The proposed simple method makes possible identification of the SS effect in the same near real-time regime as the derivation of the quiet daily curve and as level of reference for the polar cap magnetic disturbances in the calculation of the polar cap magnetic activity PC index.

Severe Space Weather: Simulations of Scaled-Up Storms

2020 ◽  
Author(s):  
Joachim Raeder ◽  
Beket Tulegenov ◽  
William Douglas Cramer ◽  
Kai Germaschewswski ◽  
Banafsheh Ferdousi ◽  
...  
Keyword(s):  
Solar Wind ◽  
Space Weather ◽  
Extreme Events ◽  
The Other ◽  
Polar Cap ◽  
Quiet Sun ◽  
Other Hand ◽  
Weather Events ◽  
The One ◽  
Extreme Space Weather Events

<p>Extreme space weather events are extremely rare, but pose a significant threat to our infrastructure. The one known event of such kind was the Carrington storm of 1859, but it was not well documented; in particular the solar wind and IMF conditions that caused it remain guesses. On the other hand, the STEREO-A observations of July 23, 2012 showed solar wind and IMF parameters that are most likely comparable to those of the Carrington event, and remind us that such extreme events are very well possible even during times of a quiet sun. Here, we use OpenGGCM simulations of such events to assess the effects of such solar wind and IMF on the magnetosphere. Precious work has shown that during the much more benign Halloween storm the nose of the magnetopause was as close as 4.9 RE, with an accordingly large polar cap. We will present simulations of a sequence of scaled-up storms with increasingly larger driving and demonstrate the further expansion of the polar cap, intensity of plasma injections, and the eventual saturation. In addition, we will show how the ionosphere potential penetrates to lower latitudes and affects the ionosphere and thermosphere at mid latitudes when the solar wind drivers become extreme.</p>

scholarly journals The Polar Cap (PC) index combination, PCC: relations to solar wind properties and global magnetic disturbances

2020 ◽  
Author(s):  
Peter Stauning
Keyword(s):  
Solar Wind ◽  
Energy Input ◽  
Source Function ◽  
Ring Current ◽  
Mean Deviation ◽  
Polar Cap ◽  
Geomagnetic Disturbances ◽  
The Real ◽  
Dst Index ◽  
Saturation Effects

The non-negative Polar Cap PCC index built from PCN (North) and PCS (South) correlates considerably better with the solar wind merging electric field and is more representative for the total energy input from the solar wind to the magnetosphere and for the development of geomagnetic disturbances than either of the hemispheric indices. The present work shows that the ring current index, Dst, to a high degree of accuracy can be derived from a source function built on the PCC indices. The integration of the PCC-based source function throughout the interval from 1992 to 2018 without attachment to the real Dst indices based on low latitude magnetic observations has generated equivalent Dst values that correlate very well (R=0.86) with the real Dst index values, which are represented with a mean deviation less than 1 nT and an overall rms deviation less than 13 nT. The precise correlation between the real and equivalent Dst values have been used to correct the PCC indices for saturation effects at high intensity disturbance conditions where the Dst index may take values beyond -100 nT. The relations between PCC and the ring current indices, Dst and ASY-H have been used, in addition, to derive the precise timing between polar cap convection processes reflected in the polar cap indices and the formation of the partial and total ring current systems. Building the ring current is considered to represent the energy input from the solar wind, which also powers auroral disturbance processes such as substorms and upper atmosphere heating. Thus, the PCC indices measuring accurately the energy input from the solar wind are powerful tools for space weather monitoring and for solar-terrestrial research.

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