• Data Set Overview
• =================

This Data Set includes Data from the Low Field Magnetometer (LFM) during the inbound Neptune Encounter beginning in the Solar Wind and continuing until the first Magnetopause Crossing. The Magnetometer are given in Heliographic Coordinates and the Data have been averaged from the 60 ms Instrument Sampling Rate to a 1.92 s resampled Rate.

The Data Set consists of the following Columns:

• 1. ctime - Decimal Seconds since 1966-01-01T00:00:00.000
• 2. pdstime - ISO Standard Time Format
• 3. Spacecraft Clock Value - m65536
• 4. Spacecraft Clock Value - mod60
• 5. Spacecraft Clock Value - fds_line
• 6. mag_id - Magnetometer ID: 1=LFM, 2=HFM
• 7. Br - Radial Component
• 8. Bt - Tangential Component
• 9. Bn - Normal Component
• 10. Bmag - Magnitude of the averaged Magnetic Field Components
• 11. avg_Bmag - Average of the Magnitude of the raw Components
• 12. lambda - Magnetic Longitude, lambda=atan(Bt/Br)
• 13. delta - Magnetic Latitude, delta=asin(Bn/avg_Bmag)
• 14. rms_br - Br Pythagorean RMS Deviation of the Component Average
• 15. rms_bt - Bt Pythagorean RMS Deviation of the Component Average
• 16. rms_bn - Bn Pythagorean RMS Deviation of the Component Average
• 17. npts - Number of Points in the Average
• 18. Data Flag - A Character String which indicates Software or Spacecraft Hardware Intervention which reduces Confidence in the Data, Null Flags represent "good" Data

• Parameters

• ==========

• Derived Parameters

• ==================

+-------------------------------------------------------------+
| Parameter Chracteristics | Value |

| Sampling Parameter Name | TIME |
| Sampling Parameter Resolution | 0.06 SECONDS |
| Minimum Sampling Parameter | 0.06 SECONDS |
| Maximum Sampling Parameter | 0.06 SECONDS |
| Sampling Parameter Interval | 1.92 SECONDS |
| Minimum Available Sampling Interval | 1.92 SECONDS |
| Data Set Parameter Name | MAGNETIC FIELD VECTOR |
| Noise Level | 0.006 NT |
| Data Set Parameter Unit | NT |
+-------------------------------------------------------------+

Magnetic Field Vector: A derived Parameter which combines the three orthogonal Magnetic Field Component Measurements.

• Measured Parameters
• ===================

Magnetic Field Component: A measured Parameter equaling the Magnetic Field Strength along a particular Axis Direction. Usually the three orthogonal Axis Components are measured by three different Sensors.

• Ancillary Data
• ==============

An ancillary Data File containing the derived Spacecraft Magnetic Field is provided with these Data at a 48 s Sample Rate. These Data provide Zero Level Offsets used in the Data Processing. Spacecraft Field Data is provided in Spacecraft Coordinates.

• Coordinate System

• =================

• Mean Inertial Heliographic 1950 (HG) Coordinates

• ================================================

+----------------------------------------------------------+
| Coordinate System Characteristics | Value |

| Coordinate System Center NAME | SUN |
| Coordinate System Reference Epoch | UNK /* 09-23-1950 */ |
+----------------------------------------------------------+

The Heliographic Coordinate System is defined in the Reference Epoch of 1950. The Unit Vectors which define the Coordinate System are as follows:

• X - Points away from the Sun toward the Ascending Node, in the Solar Equatorial Plane
• Z - Points along the Spin Axis of the Sun, positive above the Equatorial Plane
• Y - Completes the right-handed Set

Position is given in Terms of the following:

• Range (R) - The Range or R Component of the Spherical Heliographic Coordinate System is the Distance from the Position of the Sun at the Reference Epoch to the Spacecraft measured in AU.

• Latitude (LAT) - The Latitude or LAT Component of the Spherical Heliographic Coordinate System is the Angle between the Solar Equatorial Plane of the Reference Epoch measured in the Plane that contains the Solar Spin Axis of that Epoch.

• Longitude (LONG) - The Longitude or LONG Component of the Spherical Heliographic Coordinate System is Zero in the Direction of the Ascending Node at the Reference Epoch (X Direction) and increases for a Body orbiting the Sun as the Earth does.

• X - The X Component of the Heliographic Coordinate System points away from the Sun, towards the Ascending Node, and lies in the Solar Equatorial Plane.

• Y - The Y Component of the Heliographic Coordinate System is formed by the right-handed Cross Product of the X and Z Unit Vectors. It lies in the Solar Equatorial Plane and it points away from the Sun, but does not extend in the Direction of any particular Body.

• Z - The Z Component of the Heliographic Coordinate