INTRODUCTION TO SOLAR WEATHER & HF PROPAGATION. Lewis Thompson W5IFQ September 27, 2011

Transcription

1 INTRODUCTION TO SOLAR WEATHER & HF PROPAGATION Lewis Thompson W5IFQ September 27, 2011

2 PRESENTATION Ionospheric propagation NVIS Long-Range Frequency Selection (Critical Frequency & MUF) Propagation modeling Solar Weather Ionosphere (Solar Flux, Sun Spot Number) Earth s Geomagnetic Field Solar Flares CME Proton Event

3 HF Propagation Modes Free Space Line of site Ground Wave Follows Earth s curvature Ionospheric Skip Long Distance with a dead-zone NVIS (Near Vertical Incidence Sky Wave)

4 Long Distance Sky Wave

5 NVIS PROPAGATION Ionosphere F2 Layer 200 miles 100º miles Only F2 layer propagation can provide necessary range

6 NVIS Propagation

7 NVIS Frequency Selection Must operate at or below the local Critical Frequency (CF) F2 layer E layer

8 Critical Frequency Critical Frequency increases with increased ionization of F-layer Time of day Time of year Time of the 11-year sun spot cycle

9 Critical Frequency Measurement Dyess AFB Ionosonde Data (Nov. 13, 2005) Critical Frequency (MHz) Time, local (HHMM)

10 Critical Frequency Measurement Dyess AFB Ionosonde August 21, 2008 Critical Frequency, MHz Time HHMM

11 Ionosonde Data DIDBase Dyess AFB 2 nd Echo Critical Frequency MUF Chart Electron Density (Height of F2 layer)

12 TYPICAL LONG-RANGE PROPAGATION Ionosphere F2 Layer 200 miles 3000 km Both F2 & E layers propagation can be involved in multiple reflection circuits.

13 Maximum Useable Frequency (MUF) MUF (Maximum Useable Frequency) is CF/cosθ, where θ is the angle from the take-off beam to vertical. Ionosphere F2 Layer 200 miles Mid-point location θ 3000 km

14 Ionosonde Data DIDBase Dyess AFB 2 nd Echo Critical Frequency MUF Chart Electron Density (Height of F2 layer)

15 Propagation Prediction Rules of Thumb for Critical Frequency: 2 to 4 MHz at night 4 to 8 MHz in daytime Propagation prediction programs (not good for NVIS) Proplab-Pro at W6ELProp at: (free) ACE-HF at: Web information: DX Beacons Beacon Monitor -

16 Lowest Usable Frequency (LUF) Controlled by D-Layer absorption Day-time effect Function of transmit power and mode of operation Absorption is a function of 1/f 2

17 PRESENTATION Ionospheric propagation NVIS Long-Range Frequency Selection (Critical Frequency & MUF) Propagation modeling Solar Weather Ionosphere (Solar Flux, Sun Spot Number) Earth s Geomagnetic Field Solar Flares CME Proton Event

18 IONOSPHERE F2 layer F1 Layer (daytime only) E Layer D Layer

19 IONOSPHERE EUV/UV UV Monoatomic oxygen Lyman α radiation & hard X-rays EUV & soft x-rays

20 Solar Ionization Indicators Solar Flux (SF) Measure of solar radio noise at 2800 MHz (10.7 cm) Varies from 50 to 300 Increased SF leads to higher MUF 11-year cycle Does not exactly track propagation conditions Sun Spot Number (SSN) (Wolf or Zurich) Special count of # of visible sun spots Varies from 0 to year cycle 12 month running average produces best fit with propagation conditions. Increased SSN leads to higher MUF Solar Flux and SSN are mathematically related

21 Smoothed SSN

22 Daily Solar Flux & SSN

23 SOLAR EFFECTS ON PROPAGATION Ultraviolet Radiation Good X-Rays - Bad Corona Mass Ejections Bad Coronal Holes - Bad

24 SOLAR FLARES (X-Rays) Radio Blackouts (8 minute arrival) M or X class solar flare releasing X-rays SID (Sudden Ionospheric Disturbance) Caused by Extreme D-layer absorption Day time effect

25 D-Layer Absorption Day-time effect Absorption is a function of 1/f 2 Can sometimes be compensated by power or bandwidth reduction

26 X-Ray Flux Observed At Time of Net Failure (3 Aug 1348Z)

27 D-Absorption Prediction M6.0 Event, 3 Aug 1348Z (18 db of attenuation 5.2 MHz)

28 GOES X-Ray Flux (3 6 Aug. 2011) M6.0

29 D-Absorption Prediction (

30 EARTH S MAGNETIC FIELD Without Solar Wind Actual Magnetic Field

31 Coronal Mass Ejections Geomagnetic and Ionospheric Storms (1-3 day arrival) Caused by CME (Corona Mass Ejection) Coronal Holes cause smaller changes Depressed MUF and increased D absorption Indicated by increased K and A indices

32 STEREO Satellite Pair 2 Aug 2011

33 Sun Spots - Aug SWPC Classification EHO Beta, Quiet and Stable SWPC Classification FKC Beta-Gamma-Delta, C, M, X Flares SWPC Classification DKI Beta-Gamma-Delta, C, M, X flares

34 Sunspot CME (long duration M1.4 event peaking at 06:19 UTC) STEREO Ahead 07:09Z STEREO Ahead 08:09Z

35 GOES Magnetometer (Arrival of 2 Aug. CME)

36 Geomagnetic Indicators Geomagnetic Indices Measure of Earth s geomagnetic activity Increased activity means worse propagation Kp : Planetary K index varies from 0 to 9 (3-hour average) 0 to 1 quiet conditions 2 to 4 some degradation to HF propagation 5 to 6 minor storm with further degradation to HF propagation 6 to 9 major storm leading to HF blackouts Ap: Planetary A index varies 0 to 400 (average of four Kp) Effectively yesterday s magnetic field variance

37 Planetary K Index (Arrival of 2 Aug CME)

38 Ionosonde Data (2 Days Delay for 24% drop in CF) 5 August 1300Z (CF = 5.9 MHz - Normal) (MUF = 19.2 MHz) 8 August 1300Z (CF = 4.5 MHz) (MUF = 15.2 MHz)

39 Coronal Hole Effect Best display in Finland since 2006

40 Satellite Environment Plot Proton Flux from

41 3 May Solar Wind (ACE Satellite)

42 Eglin AFB Ionosonde 2 May 1300Z (9 AM CST)

43 Eglin AFB Ionosonde 3 May 1300Z (9 AM CST)

44 Proton Event Solar Radiation Storms (4 hours arrival after solar flare) Caused by High energy Protons Results in a PCA (Polar Cap Absorption) event

45 Solar & Geomagnetic Indicator Sources WWV 2, 5, 10, 15, 20 MHz at 18 pass each hour. Web site: Tx Army MARS web site Consolidated.

46 SOLAR WEATHER FORECAST ( Forecast The geomagnetic field is expected to be quiet on September 6 and most of September 7. Late on September 7 or early on September 8 the CME from the major flare early on September could reach Earth and cause active to major storm conditions.

47 QUESTIONS? Lewis Thompson W5IFQ, AAA6TX Cell (512) Home (512)