Summary: The difference in the V1 and V2 high energy counting rates appears to be real.

When plotted vs time, the V1 and V2 high energy proton rates are close to each other from 1977 to mid 1981, then again from late 1982 to early 1983. Then V2's rate increases faster than V1's and remains higher than V1's rate until the V1's crossing in 2012. When plotted vs radial distance, the two rates were close until about 9AU, around the Saturn encounter, then they diverge as V2's rate increases sharply. V2's rate started decreasing around 23AU and dipped below V1's rate around 32AU, after the V2 Neptune encounter. V2's rate increased above V1's rate by 40AU but gaps in the data make it hard to determine when. When plotted against solar ecliptic latitude, the V2 rates generally decrease from -36 deg to -3 deg. The V1 rates are fairly flat from +3 deg to +22 deg and rise slowly until roughly +32deg where there is a sharp decline followed by a steep rise.

The trends in our V1 and V2 high energy proton rates are similar to the trends in the V1 and V2 CRS Penetrating High Gain rates. Our V1 H > 211 MeV rate is suppressed when compared to the corresponding CRS rate starting around 55AU (1994) Our V2 H > 213 MeV rate is suppressed compared to the corresponding CRS rate starting around 80AU (late 2006).

V1's SAR rate is noisy, getting slightly better after 2010. V2's ALAR rate failed on 9/15/1986

Misc. notes: Our high energetic proton rates from voflux match the Fund. Tech. P31 rates well. The energetic proton rates have fewer outliers after cruise5a begins. Cruise-5a telemetry mode begins on 8/8/1990 (d220) for V1, and 6/1/1990 (d152) for V2. Plots of P31 from ftec and our CH31 rate in 1997 when both go to 0 for a few days and in 2005 show that the ftec data align with our data with no shift in time required.

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Radial distances of V1 and V2 vs time. Vertical dotted lines indicate the dates of planetary encounters for V1 and V2

Solar ecliptic latitudes of V1 and V2 vs time

V1 and V2 high energy proton count rates vs radial distance.

Add the V1 and V2 CRS Penetrating High Gain count rate to the plot. Vertical dashed lines indicate the start of a solar cycle

Multiply CRS rates by a factor to vertically align the traces at 45AU

Ratios of LECP and CRS high energy rates on V1 and V2

V1 and V2 high energy proton count rates vs solar ecliptic latitude

Add the V1 and V2 CRS Penetrating High Gain count rates to the plot

High energy proton rates from Fund. Tech. (P31 from the D33 files) and from our volfx master files

Voyager 1 SAL, SAR and ALAR rates

Voyager 2 SAL, SAR and ALAR rates

FTech V1 ALAR stopped on 8/6/1990, cruise5a started on 8/8/1990

last_pos_alar_date = dfsv1['D76'].loc[dfsv1['D76']['ALARRS10'] > 0].index.max()
Last positive V1 ALAR rate on 1990-08-06 00:13:14

FTech V2 ALAR mostly stopped on 9/15/1986 and finally stopped on 7/14/1990, cruise5a started on 6/1/1990

last_pos_alar_date = dfsv2['D76'].loc[dfsv2['D76']['ALARRS10'] > 0].index.max()
Last positive V2 ALAR rate on 1990-07-14 00:19:00

            Date_mostly  ALARRS10_mostly            Date_finally  ALARRS10_finally
1986-09-03 10:37:45.330            -1.00 1990-07-01 06:36:35.810              -1.0
1986-09-04 00:07:04.450             5.37 1990-07-02 03:30:21.280              -1.0
1986-09-05 03:09:45.130             6.07 1990-07-03 00:13:42.750              -1.0
1986-09-06 19:45:37.700             5.63 1990-07-04 04:13:42.610              -1.0
1986-09-07 00:07:04.100             5.59 1990-07-05 00:00:54.500              -1.0
1986-09-08 00:30:35.170             5.56 1990-07-06 03:07:47.160              -1.0
1986-09-09 02:54:35.040            -1.00 1990-07-07 00:13:42.250              -1.0
1986-09-10 01:19:20.560             5.06 1990-07-08 00:42:30.120              -1.0
1986-09-11 00:10:25.190             5.00 1990-07-09 00:00:53.930              48.0
1986-09-12 01:48:08.320             5.72 1990-07-10 00:00:45.860              44.4
1986-09-13 00:10:24.960             5.47 1990-07-11 00:09:53.050              43.2
1986-09-14 01:13:24.890             5.50 1990-07-12 00:09:53.060              45.0
1986-09-15 01:16:55.970             3.56 1990-07-13 00:10:21.870              42.5
1986-09-16 00:30:34.230             0.00 1990-07-14 00:19:00.260              47.8
1986-09-17 04:30:34.100             0.00 1990-07-14 12:13:41.200              -1.0
1986-09-18 08:17:43.580             0.00 1990-07-15 02:31:17.120              -1.0
1986-09-19 00:07:02.700             0.00 1990-07-17 03:38:28.850              -1.0
1986-09-20 00:08:00.140             0.00 1990-07-18 03:00:04.720              -1.0
1986-09-21 00:10:24.020             0.00 1990-07-19 03:43:45.380              -1.0
1986-09-22 00:07:02.340             0.00 1990-07-20 00:07:16.470              -1.0
1986-09-23 00:06:33.420             0.00 1990-07-21 02:37:40.320              -1.0
1986-09-24 00:23:21.300             0.00 1990-07-22 00:40:52.200              -1.0
1986-09-25 00:16:37.990             0.00 1990-07-23 01:24:32.860              -1.0
1986-09-26 00:07:01.880            -1.00 1990-07-24 00:07:15.930              -1.0
1986-09-30 01:27:07.490             0.00 1990-07-25 05:43:15.770              -1.0

Download this jupyter notebook with the python code to generate the plots. The code requires python 3.6 or later to run.

Download the data files used in the notebook. The .pd files are pandas DataFrames written with df.to_pickle().

Download ephemeris data from omniweb

Download daily filtered rate files from Fundamental Tecnologies We used these files in this notebook:

• V1yyDGDrr.CSV files in the V1yy_dailyF.ZIP archives for years 1977-1990 located in the Alternative Forms menu
• V1yyDFDrr.CSV files in the V1yy_dailyF.ZIP archives for years 1991-2006 located in the Alternative Forms menu
• V2yyDGDrr.CSV files in the V2yy_dailyF.ZIP archives for years 1977-1989 located in the Alternative Forms menu
• V2yyDFDrr.CSV files in the V2yy_dailyF.ZIP archives for years 1990-2006 located in the Alternative Forms menu
• V290DQDrr.CSV files in the V290_dailyF.ZIP archive for the year 1990 located in the Alternative Forms menu
• V1yyyy001Brr.CSV.GZ files for the years 2008-2018 in the Rates directories reached by the menus Voyager 1 Data -> yyyy
• V107001DFDrr.CSV files in the Alternative Forms dropdown for year 2007
• V2yyyy001Brr.CSV.GZ files for the years 2007, 2009-2018 in the Rates directories reached by the menus Voyager 2 Data -> yyyy
• V22008001DDrr.CSV.GZ files for the year 2008 in the DailyAvg directory reached by the menus Voyager 2 Data -> 2008

rr is the rate of interest. We use these rate files: D33 (P31), D68 (SAR), D75 (SAL) and D76 (ALAR). yy is the two digit year. yyyy is the four digit year

Download LECP flux databases from the UMD Space Physics Group

Download Voyager CRS data from the Voyager CRS Rates Time History page

last update Sep 23, 2021