September 2017 ionospheric perturbation events

This topic contains 5 replies, has 5 voices, and was last updated by  cborries 5 months, 1 week ago.

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  • #3486

    annabelehaki
    Participant

    A series of disturbances occurred in September 2017, initiated with a solar flare on 6 September. We welcome inputs with observations from the solar-magnetosphere-ionosphere coupled system, and remarks on the effects in aerospace and ground systems.

    #3487

    Cris_Tim
    Participant

    The research group of Astronomy and GEomatics (gAGE/UPC) has analyzed the impact of the solar flare occurred in September 6 th of 2017 (day of year 249) in three navigation systems: EGNOS (the European SBAS system), PPP and NRTK.

    The basic conclusion of the study is that the Solar flare, itself, shouldn’t have a direct impact in any of the 3 navigation systems: we have only found impacts in technical aspects linked indirectly to the Solar flare (i.e. the fast increasing of the STEC) and could be corrected with an adequate treatment. These impacts are:
    – Some receivers are unable to track fast changes in the STEC and present multiple loss of lock on practically all the measurements affected by the Solar flare. This is the case for the EGNOS RIMS-A receivers but not for the EGNOS RIMS-B receivers that keep up the tracking during the Solar flare.
    – In high accuracy services, as PPP or RTK, if the cycle slip detector tool is based on the geometry-free combination and works over data collected at low rate, the sudden variation of STEC can be erroneously interpreted as cycle slips. This erroneous detection degrades the navigation solutions. However, this not occur if the data were collected at higher rates.

    Full study is presented in the attached document.

    For further information, contact Miguel Juan at miguel@fa.upc.edu

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    #3500

    joannarupiewicz
    Participant

    A Coronal Mass Ejection was associated to the solar flare occurred on September 6th 2017, which produced a significant impact in the EGNOS performance on the two following days, the 7th and 8th of September. If we focus on September 8th, the values of geomagnetic index Kp and rate of TEC index can perfectly match with the EGNOS availability degradation in the North of Europe. The analysis showed that the EGNOS degradation is linked to the GPS L2 loss of lock by some receivers in the North caused by a high TEC gradients produced by the impact of the CME in the upper atmosphere. Additionally, does this CME generate any other type of irregularity in the ionosphere (e.g. TID)?

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    #4384

    DavidAF
    Participant

    The HF-Interferometry (HF-INT) method is running in near real time at the TechTIDE project website http://techtide.space.noa.gr/?page_id=3766 since 16th April 2019. Ever since then, the HF-INT has detected several periods of activity. The method can be applied in retrospective mode to evaluate the activity of large-scale Traveling Ionospheric Disturbance (LSTIDs) in the past for Europe and South Africa. Results obtained for the Space weather occurred in September 2017 provides the following observations.

    The LSTID activity as observed by the HF-INT for 7 September of 2017 reports a dominant disturbance for all the European stations with a periodicity of about 2-h and clear southward propagation occurring in the day-time and in the evening to mid-night hours. Above the Dourbes station (DB049) in Belgium, Juliusruh (JR055) in Germany, and Ebro (EB040) in Roquetes, Spain, the disturbance was first detected on September 7 at about 8:00 UT and lasted for about 6 h. It repeated again by 20:00 and lasted for about 3 h. The disturbance in the morning propagated with an azimuth of 170º (from true north) and a velocity of about 800m/s. Stations in South Africa observe a dominant disturbance with a periodicity close to 1.5-h and clear northward propagation occurring in the evening. Above the Hermanus station (HE13N), the disturbance was first detected on September 7 at about 14:00 UT and lasted for about 6-7 h. The disturbance propagated with an azimuth of 350º (from true north) and a velocity of about 300m/s. These are typical characteristics of a LSTID whose origin might be auroral.

    A LSTID activity was also observed for 8 of September of 2017 for all the European stations occurring in early hours, as continuation of the event reported for 7 of September. After 2:00 UT, we do not observe any significant activity for the European stations. However, we should notice that data availability for European stations was not good enough for the HF-INT method, mainly caused by the presence on strong Es layers that screened F-region observations. The disturbance in the night of 7-8 September with an azimuth of 180º (from true north) and a velocity of about 400m/s. South African stations report a dominant disturbance with a periodicity of about 1.5-h and northward propagation occurring in the day-time hours. Above the Louisvale station (LV12P), the disturbance was first detected on September 8 at about 10:00 UT and lasted for about 4 h. The disturbance propagated with an azimuth of 0º (from true north) and a velocity of about 450m/s. These are typical characteristics of a LSTID whose origin might be auroral.

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    #4432

    cborries
    Participant

    Large scale TID dectection methods based on GNSS measurements revealed lots of TID activity during 7th and 8th September 2017 over Europe. There were rather fast and large waves during daytime on the 7th September. During morning and afternoon hours on the 8th September slower waves are observed. They are associated to strong energy input from the solar wind.

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    #4436

    cborries
    Participant

    TEC gradients are a new product of the TechTIDE services, which are provided in near real-time since May 2019. The analysis of the TEC gradients for the September 2017 event show that weak TEC gradients are present during the generation time of LSTIDs. An example is shown in the attached image. TEC gradients in the auroral region are suggested to be used as an indicator for the generation of LSTIDs.
    TEC gradients in lower latitudes are generated by other mechanisms and are not associated with LSTID activity.

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