<?xml version="1.0" encoding="UTF-8"?>
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   <Version>2.2.6</Version>
   <NumericalData>
      <ResourceID>spase://CDPP/NumericalData/AMDA/MGS/PROXY/mgs-proxy-subsol</ResourceID>
      <ResourceHeader>

         <ResourceName>subsolar b strength</ResourceName>

         <ReleaseDate>2015-10-12T10:48:29Z</ReleaseDate>

         <Description>Subsolar field strength is calculated on an orbit-by-obit basis 
            using MGS mapping data (taken in a circular ~400 km orbit). For each orbit, 
            we take all measured field strengths when the spacecraft was at solar zenith 
            angles less than 110o. We then omit observations taken above longitudes and 
            latitudes associated with moderate or strong crustal magnetic fields. If enough 
            observations remain, then we fit the remaining data to a cos(SZA) function, and 
            extrapolate to the field magnitude at SZA=0 deg.

         </Description>
         <Acknowledgement>            
         </Acknowledgement>
         <Contact>        

            <PersonID>spase://CDPP/Person/David.Brain</PersonID>
            <Role>TechnicalContact</Role>

         </Contact>
         <InformationURL>

           <Name>MGS Proxy webpage</Name>            
           <URL>http://sprg.ssl.berkeley.edu/~brain/proxies/subsolfield.html</URL>           

         </InformationURL>       
      </ResourceHeader>
      <AccessInformation>
         <RepositoryID>spase://SMWG/Repository/CDPP/AMDA</RepositoryID>
         <Availability>Online</Availability>
         <AccessRights>Open</AccessRights>
         <AccessURL>
            <Name>AMDA at CDPP</Name>
            <URL>
                http://amda.cdpp.eu
            </URL>
         </AccessURL>

         <Format>NetCDF</Format>

         <Acknowledgement>           
         </Acknowledgement>
      </AccessInformation>

      <ProviderName>David Brain</ProviderName> 

      <InstrumentID>spase://CDPP/Instrument/AMDA/MGS/PROXY</InstrumentID>

      <MeasurementType>MagneticField</MeasurementType>

      <TemporalDescription>
         <TimeSpan>

             <StartDate>1999-04-02T15:45:28Z</StartDate>
             <StopDate>2006-10-27T14:20:34Z</StopDate>

         </TimeSpan>

       <Cadence_Min>PT1H</Cadence_Min>
       <Cadence_Max>PT2H</Cadence_Max>
     </TemporalDescription>

      <ObservedRegion>Mars</ObservedRegion>

      <Caveats>

* Upstream pressure can change on any timescale, from seconds to minutes to hours to days. Therefore, determination of the subsolar magnetic field strength may not be reliable over an entire MGS 2-hour orbital period. Please use appropriate caution when using the information on this page.
* In its ~400 km mapping orbit, MGS spends as much as 20 percent of its time above the magnetic pileup region (in the sheath), in a region where magnetic pressure is likely not the dominant pressure term. Therefore, extrapolation to a specific value of upstream dynamic pressure is much less reliable during these times. We recommend that these data be used to distinguish high pressure periods from low pressure periods.
* I use only publicly available MGS data, since those data have been fully calibrated. Therefore, the timeseries will usually be several months "behind" the current date. You can always email me to see whether the page is as up-to-date as possible.

      </Caveats>    

      <Parameter>
         <Name>|b|</Name>
         <ParameterKey>mgs_subsol_bmag</ParameterKey>
         <Description/>
         <Ucd/>
         <Units>nT</Units>
         <UnitsConversion/>
         <Field>
            <FieldQuantity>Magnetic</FieldQuantity>
         </Field>
      </Parameter>
   </NumericalData>

</Spase>