A1D4.4

From Soteria

Lead Beneficiary: UOulu

Beneficiaries involved: DTU

Due Date: month 36

Goal

Report on results of Task 4.3 Geomagnetic diagnosis of the state of the magnetosphere and space weather

Successes

The problem of the traditional Dst index which weights the disturbances of the four stations unequally was solved. The first version of the Dcx index web server was established.

Progress so far

In pursuit for consistent and reliable indices of geomagnetic storms, UOulu found out about two years ago that the traditional Dst index weights the disturbances of the four stations unequally. In fact, the Honolulu station is systematically overemphasized in the index and the Kakioka station has the smallest weight. This problem was recently solved and a related publication is under preparation. The solution of this problem also required that the calculation recipe of the Dcx index is modified. This has already been done and all the indices have been recalculated accordingly.

We have collected an extended data base of magnetic observations from 16 low to mid-latitude stations in 2000-2007 and calculated the local disturbances and the global Dst/Dcx indices for the stations of this extended network. Also, global asymmetries in disturbances were calculated and compared with earlier results. Preliminary analysis based on the extended network shows much greater local disturbances and global asymmetries than earlier detected by a smaller network. Obviously, these results will be quantified in more detail and published in near future.

UOulu is developing a web page service for the global and local Dst/Dcx indices. We have already constructed the first version of this service which includes the hourly indices based on four stations for 1932-2007 and on the extended network for 2000-2007. The service will be further developed to include more recent data, with the final aim of nearly real-time service.

DTU is working on analysis of the magnetic data from Oersted, SAC-C and CHAMP satellites in order to define new measures of geomagnetic activity that can be used in connection with the ESA mission Swarm, currently scheduled to be launched in 2011. Two investigations are performed in parallel:

• A parameterisation of the high latitude electrodynamics, i.e. location, intensity and width of R1 and R2 currents based on vector magnetic measurement from 1-2 satellites. From these parameters the WP4 focus parameters such as Joule heating and auroral oval location can be estimated. A previously developed method to calculate magnetic field disturbances observed along satellite track from these parameters, including the effect of the closing currents in the high latitude ionosphere, has been compared to observations with promising results. A collaborative project with NOVELTIS to make a computation effective automatic best-fit estimation of the parameters based on the along track magnetic field observations has been initiated.
• The development of an algorithm to derive the location of the auroral region/auroral electrojets based solely on total magnetic field intensity measurements (i.e. vector components not required). A first attempt for such an algorithm, based on the calculation of along track second order derivatives has been made and the first test cases based on Oersted data have been examined. The auroral boundary index determined from the US DMSP satellites has been acquired and will be used as reference in the further work.

List of the people working on this deliverable: UOulu: Kalevi Mursula, Arto Karinen; DTU: Susanne Vennerstrom